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Notes Class 10 2020 : Ten years board papers sample (HVB Academy, Mumbai)

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TREASURE TROVE Contents PHYSICS ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 Ph-1-13 Ph-14-25 Ph-26-36 Ph-37-48 Ph-47-58 Ph-59-74 Ph-75-87 Ph-88-97 Ph-98-108 Ph-109-123 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 Ch-124-135 Ch-136-147 Ch-148-157 Ch-158-167 Ch-168-178 Ch-179-190 Ch-191-202 Ch-203-211 Ch-212-222 Ch-223-233 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 Bio-234-244 Bio-245-254 Bio-255-266 Bio-267-278 Bio-279-290 Bio-291-302 Bio-303-313 Bio-314-326 Bio-327-339 Bio-340-354 CHEMISTRY ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper BIOLOGY ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper MATHEMATICS ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 M-355-371 M-372-385 M-386-399 M-400-411 M-412-426 M-427-445 M-446-462 M-463-482 M-483-501 M-502-521 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 H&C-522-533 H&C-534-544 H&C-545-553 H&C-554-561 H&C-562-569 H&C-570-581 H&C-582-593 H&C-594-602 H&C-603-611 H&C-612-620 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 Geo-621-631 Geo-632-640 Geo-641-651 Geo-652-661 Geo-662-671 Geo-672-685 Geo-686-697 Geo-698-707 Geo-708-717 Geo-718-730 HISTORY & CIVICS ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper GEOGRAPHY ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ENGLISH LANGUAGE-I ICSE Paper 2019 Eng-I-731-739 ICSE Question Paper 2019 (Solution for previous year papers is not given due to introduction of new pattern of the paper) ENGLISH LITERATURE-II ICSE Paper 2019 Eng-II-740-751 ICSE Question Paper 2019 (Solution for previous year papers is not given due to introduction of new syllabus) HINDI ICSE Paper 2010 Hin-752-762 ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper 2011 2012 2013 2014 2015 2016 2017 2018 2019 Hin-763-770 Hin-771-779 Hin-780-790 Hin-791-801 Hin-802-809 Hin-810-818 Hin-819-838 Hin-839-856 Hin-857-876 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 CS-877-884 CS-885-895 CS-896-911 CS-912-920 CS-921-931 CS-932-939 CS-940-946 CS-947-962 CS-963-973 CS-974-985 2010 2011 CS-986-996 CS-997-1004 COMMERCIAL STUDIES ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper COMMERCIALAPPLICATIONS ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper 2012 2013 2014 2015 2016 2017 2018 2019 CS-1005-1021 CS-1022-1031 CS-1032-1044 CS-1045-1064 CS-1065-1074 CS-1075-1088 CS-1089-1098 CS-1099-1110 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 Eco-1111-1121 Eco-1122-1132 Eco-1133-1151 Eco-1152-1160 Eco-1161-1172 Eco-1173-1183 Eco-1184-1192 Eco-1193-1200 Eco-1201-1208 Eco-1209-1218 2012 2013 2014 2015 2016 2017 2018 2019 E.A-1219-1232 E.A-1233-1242 E.A-1243-1252 E.A-1253-1262 E.A-1263-1270 E.A-1271-1280 E.A-1281-1291 E.A-1292-1302 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 CA-1303-1317 CA-1318-1328 CA-1329-1336 CA-1337-1347 CA-1348-1359 CA-1360-1367 CA-1368-1377 CA-1378-1387 CA-1388-1400 CA-1401-1409 ECONOMICS ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ECONOMICS APPLICATIONS ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper COMPUTER APPLICATIONS ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE Paper ICSE EXAMINATION QUESTION PAPER 2010 (SOLVED) PHYSICS Answers to this paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the Question Paper. The time given at the head of this paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. SECTION I (40 Marks) (Attempt all Questions) Question 1. (a) Name the device used for measuring : (i) mass (ii) weight (2) (b) A boy weights 360 N on the earth (i) What would be his approximate weight on the moon ? (ii) What is the reason for your answer ? (2) (c) A body is acted upon by a force. State two conditions under which the work done could be zero. (2) (d) A spring is kept compressed by a small trolley of mass 0.5 kg lying on a smooth horizontal surface as shown in the figure given below : When the trolley is released, it is found to move at a speed of 2m s 1 . What potential energy did the spring possess when compressed ? (2) (e) Name the subjective property (i) of sound related to its frequency. (ii) of light related to its wavelength. (2) Answer. (a) (i) Physical balance (ii) Spring balance (b) Weight of the boy on the earth = 360 N Ph- 1 2010 Ph- 2 (i) 2010 Approximate weight on the moon = 1 360 = 60 N 6 (ii) The weight on the moon has been reduced because acceleration due to gravity on the moon is to 1 th that on the surface of the earth. (_ W = mg), therefore the weight is reduced 6 1 i.e., 60 N 6 (c) We know that W = FS cosq. clearly, work done by the force will be zero if. (i) S = 0 i.e., no displacement takes place (ii) If q = 90 , then cos 90 = 0, and W = 0 i.e., when the force acts perpendicular to the direction of motion. (d) When spring is compressed, there is a potential energy stored in it. When the trolley is released the potential energy of spring is converted into kinetic energy of the trolley. \ P.E. of the spring = 1 1 mv2 = 0.5 2 2 = 1J 2 2 (e) (i) Pitch Question 2. (ii) Colour (a) (i) Why is the mechanical advantage of a lever of the second order always greater than one ? (ii) Name the type of single pulley that has a mechanical advantage greater than one. (2) (b) (i) What is meant by refraction of light ? (ii) What is the cause of refraction of light ? (c) The refractive index of diamond is 2.42;. What is meant by this statement ? (2) (d) We can burn a piece of paper by focussing the sun rays by using a particular type of lens. (i) Name the type of lens used for the above purpose. (ii) Draw a ray diagram to support your answer. (e) A ray of light enters a glass slab PQRS, as shown in the diagram. The critical angle of the glass is 42 . Copy this diagram and complete the path of the ray till it emerges from the glass slab. (2) P Q 42 Mark the angle in the diagram wherever necessary. R S Ph- 3 2010 Answer. (a) (i) The mechanical advantage of second order levers is always more than 1 because the effort arm is always longer than the load arm. (ii) A single movable pulley. (b) (i) Bending of light as it travels from one medium into another is called the refraction of light. (ii) The refraction of light takes place because the velocity of light in different media is different. (c) It means that the ratio of the velocity of light in vacuum to the velocity of light in diamond is 2.42. (d) (i) A convex lens is used to focus the sun rays on a piece of paper to burn it. A large amount of heat gets concentrated at a point and is sufficient to burn the piece of paper. (ii) The necessary ray diagram is given below. (e) The copied diagram alongwith the complete path of the ray is as shown below : N P 90 48 N D 90 S C 42 N B Q 42 r 42 i 48 48 N R A Refracted ray E Emergent ray The angle of incidence on PQ is 48 which is greater than the critical angle. Hence, total internal reflection takes place at PQ. OT is the totally reflected ray. It is incident on PS at 42 and will be refracted along TS. Question 3. (a) State two differences between light waves and sound waves. (2) (b) Two waves of the same pitch have their amplitudes in the ratio 2 : 3. (i) What will be the ratio of their loudness ? Ph- 4 2010 (ii) What will be the ratio of their frequencies ? (2) (c) Give two differences between a d. c. motor and an a. c. generator. (2) (d) Six resistances are connected together as shown in the figure. Calculate the equivalent resistance between the points A and B. (2) (e) (i) Which part of an electrical appliance is earthed ? (ii) State a relation between electrical power, resistance and potential difference in an electrical circuit. (2) Answer. (a) The two main difference are : Light Waves 1. They are electromagnetic waves and their velocity is 3 108 ms 1 . 2. They have very small wavelength. (b) (i) Sound Waves 1. These are mechanical waves and their velocity is 340 ms 1 . 2. The wavelength of sound waves is quite large compared with that of light waves. Since loudness is proportional to the square of the amplitude, therefore loundess will be in ratio of (2) 2 : (3) 2 i.e., 4 : 9. (ii) Since their pitch is the same, therefore their frequencies will be same i.e., their ratio is 1 : 1. (c) A.C. Generator 1. It is a device which converts mechanical energy into electrical energy. 2. A.C. genera tor ma kes use of two separate co-axial slip rings. 3. It works on the principle of electromagnetic induction. D.C. Motor 1. It is a device which converts electrical energy into mechanical energy. 2. It makes use of two halves of slip ring i.e ., split ring which a cts a s a commulator. 3. It works on the principle that when a conductor carrying current is placed in a magnetic field, it experiences a force. (d) Clearly, the resistance of 2W, 3W and 5W are in series. Ph- 5 \ 2010 Total resistance is 2W + 3W + 5W = 10W and the circuit reduces to as shown. Now, 10W and 10W are in parallel, there combined resistance R is : 1 1 1 2 1 = + = = R 10 10 10 5 \ R = 5W C r4 2W r5 3W E D r1 r2 2W A r6 5W B F 3W 10 W Q G r3 5W H Now, 2W, 5W, 5W are in series, therefore the net resistance is : R = 2W + 5W + 5W = 12W (e) (i) The metallic part of an electrical appliance is earthed. (ii) The required relation is P = V2 , where P is power, V the potential difference and R R is the resistance. Question 4. (a) A device is used to transform 12V a.c. to 200V a.c. (i) What is the name of this device ? (ii) Name the principle on which it works. (b) (i) Which material is the calorimeter commonly made of ? (ii) Give one reason for using this material. (c) (i) (2) (2) Name a metal that is used as an electron emitter. (ii) Give one reason for using this metal. (2) (d) Complete the following nuclear changes : Na ...Mg... + (i) 24 11 (ii) 238 92 (e) (i) U 234 90 0 -1 e Th + ..... + Energy. gy. (2) Which radiation produces maximum biological damage ? (ii) What happens to the atomic number of an element when the radiation named by you in part (i) above, are emitted ? (2) Ph- 6 2010 Answer. (a) (i) Since the device is being used to step up 12 V a.c. to 200 V a.c., it is called a step up transformer. (ii) A transformer works on the principle of mutual induction. (b) (i) The calorimeter is usually made of copper. (ii) Copper is a good conductor of heat. It therefore, takes less time to acquire the same temperature as that of the liquid in it. (c) (i) Tungsten or thoriated tungsten. (ii) High melting point and low work function. (d) (i) The completed nuclear changes are as below (use the fact that total mass number and charge numbers are always conserved in a nuclear change. 24 11 (ii) Na 24 12 Mg + U 234 90 Th + 42 He + Energy. gy. 42 He is called the a particle. 238 92 0 -1 e (e) (i) g rays. (ii) There is no change in the atomic number as g rays are uncharged. SECTION II (40 Marks) (Attempt any four Questions) Question 5. (a) (i) Define the term momentum. (ii) How is force related to the momentum of a body ? (iii) State the condition when the change in momentum of a body depends only on the change in its velocity. (3) 1 (b) A body of mass 50 kg has a momentum of 3000 kg m s . Calculate : (i) the kinetic energy of the body. (ii) the velocity of the body. (3) (c) (i) Write a relation expressing the mechanical advantage of a lever. (ii) Write an expression for the mechanical advantage of an inclined plane. (iii) Give two reasons as to why the efficiency of a single movable pulley system is always less than 100%. (4) Answer. (a) (i) Momentum of a body is defined as the quantity of motion contained in the body. It is measured by the product of mass and velocity of the body. ur dP (ii) Force is equal to the rate of change of momentum of the body i.e., F = dt (iii) The necessary condition is that mass of the body is constant and does not change with velocity. Ph- 7 (b) (i) 2010 We know that K.E.K. = (ii) Now, p = mv, v = (c) (i) 3000 3000 p2 = = 90,000 J 2 50 2m p 3000 = = 60 ms 1 m 50 effort arm M.A. of a level = load arm (ii) M.A. of an inclined plane = 1 , where q is the angle of the inclined plane. sin (iii) The efficiency of a single movable pulley is less than 100% because 1. Friction is always present. A part of the energy is always used up in overcoming friction. 2. The pulley is not weightless. Question 6. (a) A stick partly immersed in water appears to be bent. Draw a ray diagram to show the bending of the stick when placed in water and viewed obliquely from above. (3) (b) A ray of monochromatic light is incident from air on a glass slab : (i) Draw a labelled ray diagram showing the change in the path of the ray till it emerges from the glass slab. (ii) Name the two rays that are parallel to each other. (iii) Mark the lateral displacement in your diagram. (3) (c) An erect, magnified and virtual image is formed, when an object is placed between the optical centre and principal focus of a lens. (i) Name the lens. (ii) Draw a ray diagram to show the formation of the image with the above stated characteristics. (4) Answer. Eye (a) C B The stick appears to be bent upwards and seems to be shortened. This is due to refraction of light. Ph- 8 (b) 2010 Figure A Normal Incident ray i Air B r Refracted ray Glass slab N N D e nt ge er Em N L M K y ra (c) If virtual, erect and magnified image of an object placed between the optical centre and principal focus of a lens is formed, then lens must be convex. (i) Convex lens (ii) The diagram is as shown below : Question 7. (a) Two parallel rays Red and Violet travelling through air, meet the air-glass boundary as shown in the above figure : red Violet air glass (i) Will their paths inside the glass be parallel ? Give a reason for your answer. (ii) Compare the speeds of the two rays inside the glass. (3) Ph- 9 2010 (b) (i) A man stands at a distance of 68 m from a cliff and fires a gun. After what time interval will he hear the echo, if the speed of sound in air is 340 m s 1 . (ii) If the man had been standing at a distance of 12 m from the cliff would he have hear the clear echo ? (c) (i) In what unit does the domestic electric meter measure the electrical energy consumed? State the value of this unit in S.I. Unit. (ii) Why should switches always be connected to the live wire ? (iii) Give one precaution that should be taken while handling switches. (4) Answer. (a) The paths of two parallel red and violet colour rays travelling through air are as shown : Violet Red i i air glass r2 r1 Red Violet (i) Since the refractive index of glass for violet colour is more. It will bend more than the red colour as shown : The paths inside the glass will not be parallel. (ii) Velocity of red colours will be more than that of the violet colour. (b) (i) The time t after which an echo is heard is given by, 2d 2 68 = = 0.4s v 340 (ii) Man can not heard a clear echo because if man had been standing at a distance 12 m t= 2d 2 12 24 = = = 0.07 s v 340 340 which is less than 0.1 s. (c) (i) The domestic electric meter measure, the electric energy in kWh. 1 kWh = 3.6 10 6 J (ii) The switch should always be connected to the live wire, so that current is cut off to that appliance to which it is connected. (iii) The switches should not be touched with wet hand otherwise we may receive a shock. Question 8. (a) Calculate the quantity of heat that will be produced in a coil of resistance 75W if a current of 2 A is passed through it for 2 minutes. (3) then t = Ph- 10 2010 (b) (i) A substance has nearly zero resistance at a temperature of 1 K. What is such a substance called ? (ii) State any two factors which affect the resistance of a metallic wire. (3) (c) Five resistors of different resistances are connected together as shown in the figure. A 12 V battery is connected to the arrangement. Calculate : (i) the total resistance in the circuit. (ii) the total current flowing in the circuit. Answer. (a) Here, R = 75W, i = 2A, t = 2 minutes = 2 60 = 120s Now, Heat produced H = i2 Rt = 2 2 75 120J = 36000 J = 8571.4 calories. (b) (i) Superconductor (ii) The resistance of a metallic wire is affected by 1. Its area of cross-section. 2. Its temperature. (c) To solve the above Question, we have to first find the total resistance of the circuit. (i) Here we find that R1 and R2 are in parallel and their combined resistance R is given by R = 10 40 = 8W 10 + 40 Also, the resistances of 30W, 20W and 60W are in parallel and their combined resistance R is given by = 1 1 1 1 = + + R 30 20 60 2 + 3+1 6 = 60 60 Ph- 11 2010 60 = 10W 6 \ R = \ Now, R and R are in series and their combined resistance R is given by R = R + R = 8W + 10W = 18W Total resistance in the circuit = 18W R1= 10 W R2= 40 W (ii) Now, I = V 12V 2 = = A = 0.67 A R 18W 3 Question 9. (a) (i) Define the term specific latent heat of fusion of a substance. (ii) Name the liquid which has the highest specific heat capacity. (iii) Name two factors on which the heat absorbed or given out by a body depends. (3) (b) (i) An equal quantity of heat is supplied to two substances A and B. The substance A shows a greater rise in temperature. What can you say about the heat capacity of A as compared to that of B ? (ii) What energy change would you expect to take place in the molecules of a substance when it undergoes 1. a change in its temperature ? 2. a change in its state without any change in its temperature ? (3) (c) 50 g of ice at 0 C is added to 300g of a liquid at 30 C. What will be the final temperature of the mixture when all the ice has melted ? The specific heat capacity of the liquid as 2.65 J g 1 C 1 while that of water is 4.2 J g 1 C 1 . Specific latent heat of fusion of ice = 336 J g 1 . (4) Answer. (a) (i) Specific latent heat of fusion : It is defined as the heat required to melt one kilogram of a substance at its melting point without any change in temperature. (ii) Water has the highest specific heat capacity. (iii) The heat absorbed or given out by a substance depends upon (i) mass of the body, (ii) rise or fall of temperature. (b) (i) Heat absorbed by a substance is given by Ph- 12 2010 H = msq H = Heat capacity rise of temperature. Since, H is same for both A and B, it is a clear that heat capacity is inversely proportional to the rise of temperature. Since, the rise of temperature A is more its heat capacity must be less. Heat capacity of A is less than that of B. 1. The energy of the molecules of a body increases with the rise in temperature and decreases with the fall of temperature. 2. Since, temperature remains constant there is no change in the kinetic energy of the molecules. The energy given to substance to change the state of the substances increases potential energy of the molecules. \ (c) Here Ice Mass of ice = 50g Temperature of ice = 0 C Latent heat of fusion of ice = 336 Jg 1 Specific heat capacity of water = 4.2 Jg 1 C 1 Liquid Mass of the liquid = 300 g Temperature of the liquid = 30 C Specific heat capacity of liquid = 2.65 Jg 1 C 1 Let q be the final temperature of the mixture. Heat gained by 50g of ice at 0 C during its change of state to water =mL = 50 336 = 16800 J Heat gained by 50g of water when its temperature rises to q C = 50 4.2 q = 210q Total heat gained = 16800 + 210qJ Heat lost by the liquid = 300 2.65 (30 q) = 300 2.65 30 300 2.65q = 23850 795q Now, Heat gained = Heat lost 16800 + 210q = 23850 795q or 1005q = 23850 16800 = 7050 \ q= 7050 = 7 C 1005 Question 10. (a) (i) Name the radioactive radiations which have the least penetrating power. (ii) Give one use of radioisotopes. (iii) What is meant by background radiation ? (3) (b) (i) A straight wire conductor passes vertically through a piece of cardboard sprinkled with iron filings. Copy the diagram and show the setting of iron filings when a current is passed through the wire in the upward direction and the cardboard is tapped gently. Draw arrows to represent the direction of the magnetic field lines. Ph- 13 2010 (ii) Name the law which helped you to find the direction of the magnetic field lines. (3) (c) (i) State two ways by which the magnetic field of a solenoid can be made stronger. (ii) What material is used for making the armature of a electric bell ? Give a reason for using this material. (4) Answer. (a) (i) a-rays have the least penetrating power. (ii) Radioisotopes are used to study the function of fertilizer for different plants. They have also been used for developing new species of a plant by causing genetic changes. (iii) Background radiations are present at all places even in the absence of any radioactive source. The radiations are present in the atmosphere even when there is no source nearby. The source of background radiations are : (a) cosmic radiation (b) rocks in the earth which contain traces of radioactive substances (c) naturally occurring radioisotopes. (b) (i) The direction of the magnetic lines of force will be anticlockwise. The iron filings will align themselves in circular lines of force (By Right hand thumb rule.) Magnetic field lines Current (ii) Right hand thumb rule or Maxwell s cork screw rule. (c) (i) The magnetic field along the axis of a solenoid is given by B = moni Clearly, the magnetic field can be increased by 1. Increasing the current. 2. Increasing the number of turns/length. (ii) The armature of the electric bell is made of iron. This is because iron when magnetised is quickly demagnetised when the circuit is broken. Steel armature might lock up the circuit and the bell may not work. ICSE EXAMINATION QUESTION PAPER 2011 (SOLVED) PHYSICS Answers to this paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the Question Paper. The time given at the head of this paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets ( ). SECTION I (40 Marks) (Attempt all questions from this section) Question 1. (a) (i) Define one newton. (ii) Write the relation between S.I. unit and C.G.S. unit of force. (2) (b) Where does the position of centre of gravity lie for (i) a circular lamina (ii) a triangular lamina ? (2) (c) A man can open a nut by applying a force of 150 N by using a lever handle of length 0.4 m. What should be the length of the handle if he is able to open it by applying a force of 60 N? (2) (d) Name a machine which can be used to (i) multiply force (ii) change the direction of force applied. (2) (e) The diagram below shows a lever in use. Effort (E) F A B Load (L) 50 N (i) To which class of lever does it belong ? (ii) If FA = 40 cm, AB = 60 cm, then find the mechanical advantage of the lever. (2) Answer : (a) (i) Ph- 14 One newton is that force which when acting on a body of mass 1 kg, produces an acceleration of 1 ms 2 in it. 2011 Ph- 15 2011 (ii) S.I. unit of force is newton (N) and C.G.S. unit is dyne. 1N = 10 5 dyne (b) (i) Centre of lamina. (ii) The point of intersection of medians. (c) Let the second length of the handle be L. 150 0.4 = 60 L L= 150 0.4 =1m 60 \ Length of handle = 1 m (d) (i) Single movable pulley. (e) (i) Class II lever. (ii) M.A. = = (ii) Single fixed pulley. BF FA + AB = AF FA 40 + 60 100 = 2.5 = 40 40 Question 2. (a) A ball of mass 200 g falls from a height of 5 m. What will be its kinetic energy when it just reaches the ground ? (g = 9.8 m s 2 ) (2) (b) In the diagram below, PQ is a ray of light incident on rectangular glass block. (i) Copy the diagram and complete the path of the ray of light through the glass block. In your diagram, mark the angle of incidence by letter i and the angle of emergence by the letter e . (ii) How are the angle i and e related to each other ? P Q (c) A ray of monochromatic light enters a liquid from air as shown in the diagram given below. (i) Copy the diagram and show in the diagram the path of the ray of light after it strikes the mirror and re-enters the medium of air. Ph- 16 2011 (ii) Mark in your diagram the two angles on the surface of separation when the ray of light moves out from the liquid to air. (2) 45 Air 30 Liquid Plane miror (d) (i) When does a ray of light falling on a lens pass through it undeviated ? (ii) Which lens can produce a real and inverted image of an object ? (e) (i) (2) How is the refractive index of a medium related to its real depth and apparent depth? (ii) Which characteristic property of light is responsible for the blue colour of the sky ? (2) Answer : (a) K.E. = P.E. = mgh = 200 9.8 5 = 9.8 Joule 1000 (b) (i) P i Q r e (ii) i = e (c) (i), (ii) 45 45 Air 30 30 Liquid Plane miror Ph- 17 (d) (i) 2011 A ray of light passing through the optical centre of the lens passes through it undeviated. (ii) Convex lens. (e) (i) Refractive index = Real depth Apparent depth (ii) Effects of scattering. The blue or violet light due to its short wavelength is scattered more as compared to red light of long wavelength. Question 3. (a) When acoustic resonance takes place, a loud sound is heard. Why does this happen ? Explain. (2) (b) (i) Three musical instruments give out notes at the frequencies listed below. Flute : 400 Hz; Guitar : 200 Hz; Trumpet : 500 Hz. Which one of these has the highest pitch ? (ii) With which of the following frequencies does a tuning fork of 256 Hz resonate ? 288 Hz, 314 Hz, 333 Hz, 512 Hz. (2) (c) Two bulbs are marked 100 W, 220 V and 60 W, 110 V. Calculate the ratio of their resistances. (2) (d) (i) What is the colour code for the insulation on the earth wire ? (ii) Write an expression for calculating electrical power in terms of current and resistance. (2) (e) Calculate the equivalent resistance between A and B from the following diagram : (2) Answer : (a) At acoustic resonance, the amplitude of the vibration of the body becomes very large. Since loudness is proportional to the square of the amplitude, therefore, we hear a loud sound under this condition. (b) (i) Trumpet : 500 Hz. (ii) 512 Hz. Second resonance will take place. (c) We know that R = V2 P Ph- 18 2011 The resistance R1 of the first bulb, R1 = and R2 = \ 220 220 = 484W 100 110 110 1210 = = 201.67W 60 6 R1 484 6 = 2.4 = R2 1210 (d) (i) Yellow (ii) P = I2 R (e) R1 = 3 + 2 = 5W R2 = 30W R3 = 6 + 4 = 10W \ 1 1 1 1 = + + R1 R2 R3 R 1 1 1 1 = + + R 5 30 10 1 6 +1+ 3 = R 30 1 10 = R 30 R = 3W Question 4. (a) Differentiate between heat and temperature. (b) (i) (2) Define Calorimetry. (ii) What is meant by Energy degradation ? (2) (c) 200 g of hot water at 80 C is added to 300 g of cold water at 10 C. Calculate the final temperature of the mixture of water. Consider the heat taken by the container to by negligible. [specific heat capacity of water is 4200 Jkg 1 C 1 ] (2) (d) Fill in the blanks in the following sentences with appropriate words : (i) During the emission of a beta particle, the number remains the same. (ii) The minimum amount of energy required to emit an electron from a metal surface is called . (2) (e) A mixture of radioactive substances gives off three types of radiations. (i) Name the radiation which travels with the speed of light. (ii) Name the radiation which has the highest ionizing power. (2) Ph- 19 2011 Answer : (a) Heat (i) Temperature Heat is the energy of transit. (ii) Its S.I. unit is Joule. (b) (i) (i) Tempera ture is the funda menta l quantity which determines the direction of flow of heat. (ii) Its S.I. unit is Kelvin. A calorimetry is the phenomenon through which we measure the amount of heat gained or lost by a body when it is mixed with other body. (ii) It is the transformation of energy into some form in which it is less available for doing work. (c) Let the final temperature be T C. By the principle of calorimetry, we know Heat lost = Heat gained 200 4200 (80 T) = 1000 300 4200 (T 10) 1000 2 (80 T) = 3 (T 10) 160 2T = 3T 30 160 + 30 = 3T + 2T 5T = 190 \ T= 190 = 38 C 5 (d) (i) Mass number (ii) Work function (e) (i) g-rays (ii) Alpha particle SECTION II (40 Marks) (Attempt any four questions from this section) Question 5. (a) (i) What is meant by an ideal machine ? (ii) Write a relationship between the mechanical advantage (M.A.) and velocity ratio (V.R.) of an ideal machine. (iii) A coolie carrying a load on his head and moving on a frictionless horizontal platform does no work. Explain the reason why. (3) (b) Draw a diagram to show the energy changes in an oscillating simple pendulum. Indicate in your diagram how the total mechanical energy in it remains constant during the oscillation. (3) (c) A uniform metre scale can be balanced at the 70.0 cm mark when a mass of 0.05 kg is hung from the 94.0 cm mark. Ph- 20 (i) 2011 Draw a diagram of the arrangement. (ii) Find the mass of the metre scale. (4) Answers : (a) (i) In an ideal machine, the work output is equal to the work input i.e., the efficiency of an ideal machine is 100%. (ii) Efficiency = M.A. V.R. In an ideal machine, ratio = 1 : 1 (iii) Coolie does not move under the influence of a force i.e., frictional force is zero. The force applied by him to lift the load is perpendicular to displacement. (b) O Total energy K.E. P.E. = mgh K.E= 0 Energy P.E. = mgh K.E = 0 C P.E. B h h A K.E. = mgh P.E. = 0 Height above ground The variation of potential and kinetic energy is as shown. The total energy remains constant. (c) (i) 9cm 50cm 70cm 94cm 100cm F W (ii) According the principle of moments W (70 50) = 0.05 (94 70) W 20 = 0.05 24 Weight of the metre scale = 24 0.05 = 0.06 kg 20 Question 6. (a) (i) State the laws of refraction of light. (ii) Write a relation between the angle of incidence (i), angle of emergence (e), angle of prism (A) and angle of deviation (d) for a ray of light passing through an equilateral prism. (3) (b) (i) Suggest one way, in each case, by which we can detect the presence of : 1. Infrared radiations. (ii) Give one use of Infrared radiations. 2. Ultraviolet radiations. (3) Ph- 21 2011 (c) An object is placed in front of a lens between its optical centre and the focus and forms a virtual, erect and diminished image. (i) Name the lens which formed this image. (ii) Draw a ray diagram to shows the formation of the image with the above stated characteristics. (4) Answer : (a) (i) Laws of Refraction : (a) The incident ray, the refracted ray and the normal at the point of incidence, all lie in the same plane. (b) The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for the pair of given media. (ii) i + e = A + d (b) (i) It is the portion of spectrum : (a) Just beyond the red end. A blackened thermometer shows a much larger rise of temperature when placed in the infrared region. (b) Just before the violet end. These are detected by the silver chloride solution which turns violet and finally black in the ultraviolet light. (ii) They are used in photography at night. (c) (i) Concave lens C (ii) A B A F2 D D O F1 Question 7. (a) (i) Name the type of waves which are used for sound ranging. (ii) Why are these waves mentioned in (i) above, not audible to us ? (iii) Give one use of sound ranging. (3) (b) A man standing 25 m away from a wall produces a sound and receives the reflected sound. (i) Calculate the time after which he receives the reflected sound if the speed of sound in air is 350 ms 1. (ii) Will he man be able to hear a distinct echo ? Give a reason for your answer. (c) (i) (3) Name two safety devices which are connected to the live wire of a household electrical circuit. (ii) Give one important function of each of these two devices. (4) Ph- 22 2011 Answer. (a) (i) Ultrasonic waves. (ii) Because their frequency lies beyond the limits of audibility (20 Hz 20,000 Hz). (iii) To locate the position of the object under water and to find the depth of sea. (b) (i) Time = 2d 2 25 = = 0.14 sec v 350 (ii) Yes, because distance is more than 17 m and time period is 0.14 sec. (c) (i) Connected devices are switches and fuses to live wire. (ii) Fuse : It is a safety device which is used to limit current in an electric circuit. Switch : Its main function is either to connect or to disconnect an electric appliance in an electric circuit. Question 8. (a) (i) Draw a graph of Potential difference (V) versus Current (I) for an ohmic resistor. (ii) How can you find the resistance of the resistor from this graph ? (iii) What is a non-ohmic resistor ? (3) (b) (i) An electric bulb is marked 100 W, 250 V. What information does this convey ? (ii) How much current will the bulb draw if connected to a 250 V supply ? (3) (c) Three resistors are connected to a 12 V battery as shown in the figure given below : P.D. in volts (i) What is the current through the 8 ohm resistor ? (ii) What is the potential difference across the parallel combination of 6 ohm and 12 ohm resistor ? (iii) What is the current through the 6 ohm resistor ? (4) Answer : (a) (i) I (in amp.) Ph- 23 2011 (ii) The reciprocal of the I-V graph shown in the figure gives the resistance of the resistor. (iii) Resistor which do not obey ohm s law (i.e., V I) are called non-ohmic resistors. (b) (i) P = 100 W V = 250 V It tells us that it will consume 100 watt at 250 V. (ii) R = = \ (c) (i) 250 250 = 625W 100 I= = V2 P V R 250 = 0.4 A 625 Resistance of 12W, 6W parallel combination = 12 6 = 4W 18 The combined resistance of the circuit = 8 + 4 = 12W \ Current through 8W resistance = 12V = 1A 12 (ii) Potential difference across the 12W 6W parallel combination is = 4 1 = 4V (iii) Current through 6W resistor = 1 12 12 2 = = A 6 + 12 18 3 Question 9. (a) (i) Explain why the weather becomes very cold after a hail storm. (ii) What happens to the heat supplied to a substance when the heat supplied causes no change in the temperature of the substance ? (3) (b) (i) When 1 g of ice at 0 C melts to form 1 g of water at 0 C then, is the latent heat absorbed by the ice or given out by it ? (ii) Give one example where high specific heat capacity of water is used as a heat reservoir. (iii) Give one example where high specific heat capacity of water is used for cooling purposes. (3) (c) 250 g of water at 30 C is present in a copper vessel of mass 50 g. Calculate the mass of ice required to bring down the temperature of the vessel and its contents to 5 C. Specific latent heat of fusion of ice = 336 10 3 J kg 1 Specific heat capacity of copper vessel = 400 J kg 1 C 1 Specific heat capacity of water = 4200 J kg 1 C 1 (4) Ph- 24 2011 Answer : (a) (i) (b) (c) As the ice starts melting after a hail storm, it absorbs latent heat of fusion from the surrounding air. This leads to the cooling of atmosphere. (ii) Heat supplied to a substance during its change of state is called latent heat. It is used up in increasing the potential energy of the molecules of the substance and in doing work against external pressure if there is an increase in volume. Hence there is no change of temperature. (i) Water at 0 C has more heat than ice at 0 C. This is because each gram of ice absorbs nearly 336 J of heat when it melts into water at 0 C. (ii) Hot water bottles are used for fomentation since water does not cool quickly. (iii) It is used as coolant by flowing it in pipes around the heated part of machines. According to the principle of calorimetry we know, Heat gained = Heat lost m 336 + m 4.2 5 = 250 4.2 (30 5) + 50 0.4 (30 5) 336 m + 21 m = 250 105 + 50 10 357 m = 26250 + 500 \ m= 26750 = 74.9 g 357 Question 10. (a) (i) State two properties which a substance should possess when used as a thermionic emitter. (ii) When an alpha particle gains two electrons it becomes neutral and becomes an atom of an element which is a rare gas. What is the name of this rare gas ? (3) (b) (i) Define radioactivity. (ii) What happens inside the nucleus that causes the emission of beta particle ? (iii) Express the above change in the form of an equation. (3) (c) (i) Name a device which is commonly used to convert an electrical signal into a visual signal. (ii) The nucleus 202 84 X emits an alpha particle and forms the nucleus Y. Represent this change in the form of an equation. (iii) What changes will take place in the mass number and atomic number of nucleus Y if it emits gamma radiations ? (4) Answer. (a) (i) (1) Low work function. (2) High melting point. (ii) Helium atom (b) (i) Radioactivity is self spontaneous disintegration of a heavy nucleus in a, b, and g radiation. Ph- 25 2011 (ii) The atomic number increases by one. (iii) (c) (i) (ii) A ZX -emission A Z+1 Y + 0 -1 e A cathode ray tube. 202 84 X -emission 198 82 Y (iii) There will be no change. + 42 He ICSE EXAMINATION QUESTION PAPER 2012 (SOLVED) Time : 1 hours 80 Marks Answers to this paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the Question Paper. The time given at the head of this paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. SECTION I (40 Marks) (Attempt all questions from this section) Question 1. (a) (i) Define 1 kgf. (ii) How is it related to the S.I. unit of force ? [2] (b) (i) What are non-contact forces ? (ii) How does the distance of separation between two bodies affect the magnitude of the non-contact force between them ? [2] (c) A boy of mass 30 kg is sitting at a distance of 2 m from the middle of a see-saw. Where should a boy of mass 40 kg sit so as to balance the sea-saw ? [2] (d) (i) What is meant by the term moment of force ? (ii) If the moment of force is assigned a negative sign then will the turning tendency of the force be clockwise or anticlockwise ? [2] (e) A ball is placed on a compressed spring. When the spring is released, the ball is observed to fly away. (i) What form of energy does the compressed spring possess ? (ii) Why does the ball fly away ? [2] Answer. (a) (i) Compressed spring The force with which a mass of 1 kg is attracted towards the centre of the earth, due to the acceleration due to gravity is called 1 kgf. (ii) 1 kgf = 1 kg acceleration due to gravity = 1 kg 9.8 ms 2 = 9.8 N (b) (i) The forces which do act on bodies without being physically touched are called the non-contact forces. (ii) The magnitude of non-contact forces acting between the two bodies is inversely proportional to the square of distance between the mass centres of the two bodies. Ph- 26 2012 Ph- 27 2012 (c) Let x be the distance of 40 kg boy from the middle of see-saw. \ Moments due to 40 kg boy = Moments due to 30 kg boy 40 kg x = 30 kg 2 m \ x= 30 kg 2 m = 1.5 m 40 kg (d) (i) The turning effect of a force about a fixed point or a fixed axis is called moment of force. (ii) Negative sign of the moment of force implies that turning tendency of the force is in anticlockwise direction. (e) (i) The compressed spring possesses potential energy. (ii) The potential energy of the spring on releasing changes to kinetic energy. It is the kinetic energy which makes the ball to fly away. Question 2. (a) (i) State the energy conversion taking place in a solar cell. (ii) Give one disadvantage of using a solar cell. [2] (b) A body of mass 0.2 kg falls from a height of 10 m to a height of 6 m above the ground. Find the loss in potential energy taking place in the body. [g = 10 ms 2 ] [2] (c) (i) Define the term refractive index of a medium in terms of velocity of light. (ii) A ray of light moves from a rare medium to a dense medium as shown in the diagram below. Write down the number of the ray which represents the partially reflected ray. [2] Ray 1 Ray 2 Rare medium Dense medium Ray 3 (d) You are provided with a printed piece of paper. Using this paper how will you differentiate between a convex lens and a concave lens ? [2] (e) A ray of light incident at an angle of incidence i passes through an equilateral glass prism such that the refracted ray inside the prism is parallel to its base and emerges from the prism at an angle of emergence e . (i) How is the angle of emergence e related to the angle of incidence i ? (ii) What can you say about the value of the angle of deviation in such a situation ? [2] Answer. (a) (i) In a solar cell, the light energy directly changes to electric energy. Ph- 28 2012 (ii) Solar cell does not produce electric energy during night or in darkness. (b) Loss in potential energy = mass g loss of height = 0.2 kg 10 ms 2 4 m = 8 J (c) (i) Refractive index of a medium is the ratio of velocity of light in vacuum or air to the velocity of light in a given medium. (ii) Ray 2, represents partially reflected ray. (d) Hold each of the lens 5 cm above the printed paper and look for the image. In case of convex lens the print appears enlarged. However, in case of concave lens, the print appears diminished. (e) (i) Angle of incidence is equal to the angle of emergence. (ii) The angle of deviation is minimum in this particular case. Question 3. (a) (i) What is meant by Dispersion of light ? (ii) In the atmosphere which colour of light gets scattered the least ? [2] (b) Which characteristic of sound will change if there is a change in (i) its amplitude (ii) its waveform. [2] (c) (i) Name one factor which affects the frequency of sound emitted due to vibrations in an air column. (ii) Name the unit used for measuring the sound level. [2] (d) An electrical appliance is rated at 1000 kVA, 220V. If the appliance is operated for 2 hours, calculate the energy consumed by the appliance in : (i) kWh (ii) joule (e) Calculate the equivalent resistance between P and Q from the following diagram : [2] 2 Answer. (a) (i) The phenomenon due to which white light splits into component colours on passing through a prism is called dispersion of light. (ii) Red colour scatters least in the atmosphere. (b) (i) With the change in amplitude, the loudness of sound changes. (ii) With the change in waveform the quality of sound changes. (c) (i) The length of vibrating air column affects its frequency. More the length of vibrating air column, lesser is its frequency. (ii) Decibel (dB) is the unit used for measuring sound level. Ph- 29 2012 (d) (i) Energy consumed in kWh = 1000 kVA 2h = 2000 kWh. (ii) Energy consumed in Joules = 1000 1000 VA 2 3600 s = 7,200,000,000 J (e) Resistance of two 10W resistance in series = 10 + 10 = 20W \ Equivalent resistance of 20W in parallel with 5W resistance 1 1 1 1+ 4 5 1 R p = 20 + 5 = 20 = 20 = 4 \ Rp = 4W \ Resistance between P and Q in series = 3W + 4W + 2W = 9W Question 4. (a) (i) What is an a.c. generator or Dynamo used for ? (ii) Name the principle on which it works. (b) Differentiate between heat capacity and specific heat capacity. [2] [2] (c) A hot solid of mass 60 g at 100 C is placed in 150 g of water at 20 C. The final steady temperature recorded is 25 C. Calculate the specific heat capacity of the solid. [Specific heat capacity of water = 4200 J kg 1 C 1 ] [2] (d) (i) What is the value of the speed of gamma radiations in air or vacuum ? (ii) Name a material which exhibits fluorescence when cathode rays fall on it. [2] (e) Give any two important sources of background radiation. Answer. (a) (i) Dynamo is used for conversation of mechanical energy into electric energy. [2] (ii) Principle of A.C. Generator : When a conductor is rotated in a magnetic field, the magnetic flux linked with it changes and e.m.f. is induced in the coil. (b) Heat capacity is the amount of heat required to raise the temperature of a given mass of substance through 1 K or (1 C). Specific heat capacity is the amount of heat required to raise the temperature of 1 kg (or 1g) of a substance through 1K (1 C). (c) msolid Csolid qfall = mwater Cwater qR 60 150 kg Csolid 75 C = kg 4200 Jkg 1 C 1 5 C 1000 1000 \ Csolid = 150 4200 5 1000 J kg 1 C 1 = 700 J kg 1 C 1 1000 60 75 (d) (i) The speed of gamma rays (g) is 3 108 ms 1 . (ii) Zinc sulphide, Barium platinocyanide show fluorescence when cathode rays fall on it. (e) (i) The radioactive emissions given out by the earth. (ii) Sources are K-40, C-14 and Radium contained inside our body. Ph- 30 2012 SECTION II (40 Marks) (Attempt any four questions from this Section) Question 5. (a) (i) Which of the following remains constant in uniform circular motion : Speed or Velocity or both ? (ii) Name the force required for uniform circular motion. State its direction ? [3] (b) (i) State the class of levers and the relative positions of load (L), effort (E) and fulcrum (F) in each of the following cases. 1. a bottle opener 2. Sugar tongs. (ii) Why is less effort needed to lift a load over an inclined plane as compared to lifting the load directly ? [3] (c) (i) A moving body weighing 400 N possesses 500 J of kinetic energy. Calculate the velocity with which the body is moving. (g = 10 ms 2 ) (ii) Under what condition will a set of gears produce 1. a gain in speed 2. Answer. (a) (i) a gain in torque. [4] Speed remains constant during uniform circular motion. (ii) Centripetal force. It is always directed towards the centre of the circular path. (b) (i) 1. In case of bottle opener the load (L) acts in the middle of metal crown, the fulcrum (F) at the edge of metal crown and effort (E) at the end of the handle. It is a lever of second order. 2. Sugar tongs is a lever of third order. The sugar cube at the ends of tongs acts as load (L), the effort (E) acts in the middle and fulcrum (F) acts at its end. (ii) Here, mechanical advantage = (c) (i) \ 1 1 sin q = sin Mechanical advantage If a body rises 1 m vertically, when it moves along the inclined plane by 100 m. Then sin q = 1/100. Higher the magnitude of the gradient, more difficult, more difficult is the slop to climb and vice-versa. Thus keeping gradient as low as possible which helps in using lesser effort for lift a load over inclined plane as compared to lifting the load directly. Force acting on body (F) = mg 400 N = m 100 ms 2 Mass of body (m) = 400 N 10 ms 2 = 40 kg. Kinetic energy of body (KE) = 1 mv 2 2 Ph- 31 2012 500 J = v2 = \ v= 1 40 kg v 2 2 500 2 2 ms 20 25 = 5ms 1 (ii) 1. When the radius of driven wheel is less than the driving wheel. 2. When the radius of driven wheel is more than the driving wheel. Question 6. (a) (i) What is meant by the term critical angle ? (ii) How is it related to the refractive index of the medium ? (iii) Does the depth of a tank of water appear to change or remain the same when viewed normally from above ? [3] (b) A ray of light PQ is incident normally on the hypotenuse of a right angled prism ABC as shown in the diagram given alongside : P A Q B C (i) Copy the diagram and complete the path of the ray PQ till it emerges from the prism. (ii) What is the value of the angle of deviation of the ray ? (iii) Name an instrument where this action of the prism is used. [3] (c) A converging lens is used to obtain an image of an object placed in front of it. The inverted image is formed between F2 and 2F2 of the lens. (i) Where is the object placed ? (ii) Draw a ray diagram to illustrate the formation of the image obtained. [4] Answer. (a) (i) The angle of incidence in a denser medium for which angle of refraction in rarer medium is 90 is called critical angle. (ii) Refractive index (m) = 1 sin C (iii) The depth of tank remains same when viewed normally from above. Ph- 32 2012 P (b) (i) A Q U R 45 45 T 45 45 B S C (ii) The ray deviates through 180 . (iii) Binoculars use this action of right angled prism. (c) (i) The object is anywhere between 2F1 and infinity. (ii) A O B 2F1 F2 B1 2F F1 A1 Converging lens Question 7. (a) (i) What is meant by Resonance ? (ii) State two ways in which Resonance differs from Forced vibrations. (b) (i) [3] A man standing between two cliffs produces a sound and hears two successive echoes at intervals of 3 s and 4 s respectively. Calculate the distance between the two cliffs. The speed of sound in the air is 330 ms 1 . (ii) Why will an echo not be hears when the distance between the source of sound and the reflecting surface is 10 m ? [3] (c) The diagram alongside shows the displacement-time graph for a vibrating body. (i) Name the type of vibrations produced by the vibrating body. (ii) Give one example of a body producing such vibrations. (iii) Why is the amplitude of the wave gradually decreasing ? (iv) What will happen to the vibrations of the body after some time ? Ph- 33 2012 Answer. (a) (i) The phenomenon due to which the natural frequency of a given body corresponds to the frequency of sound impressed on it, such that it rapidly starts vibrating is called resonance. (ii) 1. The resonance takes place only when the natural frequency of a given body is equal to the frequency of sound impressed on it, whereas during forced vibration a body is forced to vibrate with the frequency of sound impressed on it. 2. Loud sound is produced during resonance, but not in case of forced vibrations. (b) (i) Distance between two cliffs = v t 300 ms -1 7 s = = 1155 m. 2 2 (ii) The persistence of sound on ear drum is 1/10 of a second. The echo can be heard if the minimum distance of the source of sound from the vibrating body is 17 m. As the distance is only 10 m, therefore, no echo is produced. (c) (i) Transverse vibrations are produced which are gradually damped. (ii) A stretched string of a guitar. (iii) As the energy of wave is dissipated its amplitude decreases. (iv) The body will stop vibrating. Question 8. (a) (i) A cell is sending current in an external circuit. How does the terminal voltage compare with the e.m.f. of the cell ? (ii) What is the purpose of using a fuse in an electrical circuit ? (iii) What are the characteristic properties of fuse wire ? [3] (b) (i) Write an expression for the electrical energy spent in the flow of current through an electrical appliance in terms of I, R and t. (ii) At what voltage is the alternating current supplied to our houses ? (iii) How should the electric lamps in a building be connected ? [3] (c) Three resistors are connected to a 6 V battery as shown in the figure given alongside : Calculate : (i) the equivalent resistance of the circuit. (ii) total current in the circuit. (iii) potential difference across the 7.2 W resistor. Ph- 34 2012 Answer. (a) (i) Terminal voltage is slightly less than the e.m.f. of the cell. (ii) The fuse wire melts and stops the flow of electric current in a given circuit, in case the circuit is overloaded or short circuited. (iii) 1. Fuse wire should have low melting point around 200 C. 2. Fuse wire should have high electrical resistance. (b) (i) Electrical energy (E) = I2 .R.t. (ii) Alternating current is supplied at 220V for domestic consumption. (iii) All lamps should be connected in parallel. (c) (i) Resistance of 8W and 12W resistors in parallel. 1 1 1 3+ 2 5 R p = 8 + 12 = 24 = 24 \ Rp = 24 = 4.8W 5 Equivalent resistance of circuit = Rp + 7.2W = 4.8W + 7.2W = 12W (ii) Current in circuit I = V 6V = = 0.5 A. R 12W (iii) Potential difference across 7.2W resistor V = I.R = 0.5 A 7.2W = 3.60V Question 9. (a) (i) Write an expression for the heat energy liberated by a hot body. (ii) Some heat is provided to a body to raise its temperature by 25 C. What will be the corresponding rise in temperature of the body as shown on the kelvin scale ? (iii) What happens to the average kinetic energy of the molecules as ice melts at 0 C ? [3] (b) A piece of ice at 0 C is heated at a constant rate and its temperature recorded at regular intervals till steam is formed at 100 C. Draw a temperature time graph to represent the change in phase. Label the different parts of your graph. [3] (c) 40 g of ice at 0 C is used to bring down the temperature of a certain mass of water at 60 C to 10 C. Find the mass of water used. [Specific heat capacity of water = 4200 J kg 1 C 1 ] [Specific latent heat of fusion of ice = 336 103 J kg 1 ] [4] Answer. (a) (i) Heat liberated by a body = mass sp. heat capacity fall in temperature = m C qfall (ii) The rise in temperature on kelvin scale will be 25 K. Ph- 35 2012 (iii) The average kinetic energy of the molecules remains same. (b) D Temp ( C) 100 0 C A B E C Time (s) (c) Heat absorbed by ice to form water at 0 C = 40 g 336 Jg 1 = 13440 J. Heat absorbed by water at 0 to attain temperature of 10 C = mCqR = 40 g 4.2 Jg 1 C 1 10 C = 1680 J. \ Total heat absorbed = (13440 + 1680) J = 15120 J Heat given out by water at 60 C = mCqF = m 4.2 Jg 1 C 1 50 C = 210 m J g 1 Now, Heat given out = Heat absorbed \ 210 m Jg 1 = 15120 J \ m= 15120 g = 72 g. 210 Question 10. (a) The diagram alongside shows a current carrying loop or a circular coil passing through a sheet of cardboard at the points M and N. The sheet of cardboard is sprinkled uniformly with iron filings. (i) Copy the diagram and draw an arrow on the circular coil to show the direction of current flowing through it. (ii) Draw the pattern of arrangement of the iron filings when current is passed through the loop. [3] (b) (i) Draw a simplified labelled diagram of a hot cathode ray tube. (ii) Name a common device where a hot cathode ray tube is used. [3] (c) A certain nucleus X has a mass number 14 and atomic number 6. The nucleus X changes to 7 Y14 after the loss of a particle. (i) Name the particle emitted. Ph- 36 2012 (ii) Represent this change in the form of an equation. (iii) A radioactive substance is oxidized. What change would you expect to take place in the nature of its radioactivity ? Give a reason for you answer. [4] Answer. (a) (i) and (ii) (b) (i) (ii) Hot cathode ray tube is used in monitors in computers. (c) (i) The particle emitted is beta particle. 14 (ii) 6 Y14 + b 7Y (iii) No change will take place in its rate of activity. It is because oxidation is a chemical change which takes at electron level. It has nothing to do with nucleus of the atom. ICSE EXAMINATION QUESTION PAPER 2013 (SOLVED) (Time : 1 1/2 hours) (M.Marks 80) Answers to this Paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the Question Paper, The time given at the head of this Paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. Section I (40 Marks) Attempt all questions from this Section. Question 1 (a) Give any two effects of a force on a non-rigid body. Fixed end (b) One end of a spring is kept fixed while the other end F is stretched by a force as shown in the diagram. (i) Copy the diagram and mark on it the direction of the restoring force. (ii) Name one instrument which works on the above principle. (2) (c) (i) Where is the centre of gravity of a uniform ring situated ? (ii) The position of the centre of gravity of a body remains unchanged even when the body is deformed. State whether the statement is true or false. (2) 1 (d) A force is applied on a body of mass 20 kg moving with a velocity of 40 ms . The body attains a velocity of 50 ms 1 in 2 seconds. Calculate the work done by the body. (2) (e) A type of single pulley is very often used as a machine even though it does not give any gain in mechanical advantage. (i) Name the type of pulley used. (ii) For what purpose is such a pulley used ? (2) Answer. (a) (i) A force can bring about change in the state of rest or uniform motion of a body. (ii) A force can change the shape of dimensions of a body. (b) (i) F Restoring force F (ii) Spring balance. Fixed end (c) (i) The centre of gravity of a uniform ring is its centre. (ii) False (d) Acceleration of body (a) = n - u (50 - 40) ms -1 = = 5 ms 2 t 2s Distance covered by body while accelerating, S = ut + 1 1 at2 = 40 2 + 5 2 2 = 80 + 10 = 90 m 2 2 Force possessed by body, F = m.a = 20 (kg) 5 ms 2 = 100 N Ph- 37 2013 Ph- 38 2013 \ Work done by the body, W = F S = 100 N 90 m = 9000 J (e) (i) Single fixed pulley. (ii) It helps in changing the direction of applying efforts. Question 2. (a) (i) In what way does an Ideal machine differ from a Practical machine ? (ii) Can a simple machine act as a force multiplier and a speed multiplier at the same time?(2) (b) A girl of mass 35 kg climbs up from the first floor of a building at a height 4 m above the ground to the third floor at a height 12 m above the ground. What will be the increase in her gravitational potential energy ? (g = 10 ms 2). (c) Which class of lever found in the human body is being used by a boy (i) when he holds a load on the palm of his hand. (ii) when he raises the weight of his body on his toes ? (d) A ray of light is moving from a rarer medium to a denser medium and strikes a plane mirror placed at 90o to the direction of the ray as shown in the diagram. (i) Copy the diagram and mark arrows to show the path of the ray of light after it is reflected from the mirror. (ii) Name the principle you have used to mark the arrows to show the direction of the ray.(2) (e) (i) The refractive index of glass with respect to air is 1.5. What is the value of the refractive index of air with respect to glass ? (ii) A ray of light is incident as a normal ray on the surface of separation of two different mediums. What is the value of the angle of incidence in this case ? (2) Answer (a) (i) An ideal machine is the one whose parts are frictionless as well as weightless, such that its mechanical advantage is equal to its velocity ratio. A practical machine is the one whose parts are neither frictionless nor weightless. Furthermore, its mechanical advantage is always less than its velocity ratio. (ii) No, it can be either speed multiplier or force multiplier. (b) Mass of girl (m) = 35 kg Height gained by girl (h) = (12 4) = 8 m \ Increase in gravitational potential energy = mgh = 35 (kg) 10 ms 2 8 m Rarer medium = 2800 J Denser medium (c) (i) Lever of third order. (ii) Lever of second order (d) (i) (ii) The principle is the law of reversibility of light 90 Mirror Ph- 39 2013 g (e) (i) ma = a 1 1 2 = = = 0.67 (Appox.) m g 1 .5 3 (ii) Angle of incidence is zero. Question 3 (a) A bucket kept under a running tap is getting filled with water. A person sitting at a distance is able to get an idea when the bucket is about to be filled. (i) What change takes place in the sound to give this idea ? (ii) What causes the change in the sound ? (2) (b) A sound made on the surface of a lake takes 3 s to reach a boatman. How much time will it take to reach a diver inside the water at the same depth ? [Velocity of sound in air = 330 ms 1 ; Velocity of sound in water = 1450 ms 1] (2) (c) Calculate the equivalent resistance between the points A and B for the following combination of resistors : (2) (d) You have been provided with a solenoid AB. A B (i) What is the polarity at end A ? (ii) Give one advantage of an electromagnet over a permanent magnet. (2) (e) (i) Name the device used to protect the electric circuits from overloading and short circuits. (ii) On what effect of electricity does the above device work ? (2) Answer (a) (i) The sharp pitched sound slowly changes to low pitched sound as the bucket gets filled. The sound almost dies when the bucket is completely filled. (ii) As the length of vibrating air column decreases due to the water, the frequency of the sound changes. (b) Distance covered by the sound to reach boatman = 330 ms 1 3 s = 990 m \ Distance of diver from the source of sound = 990 m Ph- 40 2013 990 m 990 \ Time taken by the sound to reach diver = 1450 ms 1 = 145 s = 0.68 s (Appox.). (c) Resistance of three 4 W resistors in series = 4 3 = 12 W Resistance of three 2 W resistors in series = 2 3 = 6 W \ Equivalent resistance of 12 W , 6 W and 4 W in parallel. 1 1 1 1 1+ 2 + 3 6 1 = + + = = = R p 12 6 4 12 12 2 Rp = 2 W \ Equivalent resistance of 5 W , 2 W and 6 W in series. Rs = (5 + 2 + 6) W = 13 W (d) (i) Polarity at the end A is NORTH. (ii) An electromagnet s strength can be increased by increasing the flow of current in the coil, which is not possible in case of a permanent magnet. (e) (i) Electric fuse. (ii) It works on the heating effect of electric current. Question 4 (a) Define the term Heat capacity and state its S.I. unit. (2) (b) What is meant by Global warming ? (2) (c) How much heat energy is released when 5 g of water at 20oC changes to ice at 0oC? [Specific heat capacity of water = 4.2 Jg 1 oC 1 ; Specific latent heat of fusion of ice = 336 g 1] (2) (d) Which of the radioactive radiations (i) can cause severe genetical disorders. (ii) are deflected by an electric field ? (e) A radioactive nucleus undergoes a series of decays according to the sequence a a b X3. X2 X1 X If the mass number and atomic number of X3 are 172 and 69 respectively, what is the mass number and atomic number of X ? Answer (a) Heat capacity : The amount of heat energy required to raise the temperature of a given mass of a substance through 1 K (or 1oC) is called its heat capacity. S.I. unit of heat capacity is JK 1. (b) The rise in average temperature of the atmosphere around the earth, due to the trapping of radiant solar heat due to carbon dioxide and chloroflurocarbons is called global warming. (c) Heat energy released in cooling water to 0oC = mc q f = 5 4.2 20 = 420J Heat energy released in freezing water = mL = 5 336 = 1680 J \ Total heat energy released = (1680 + 420) J = 2100 J (d) (i) Gamma radiations (ii) Alpha and beta radiations (e) 172 69 X 3 +a 176 71 X2 ; 176 71 X 2 +a 180 73 X1 180 73 X 1 +b Thus, mass number of X is 180 and atomic number 72 ; 180 72 X Ph- 41 2013 SECTION II (40 Marks) Attempt any four questions from this Section. Question 5. (a) (i) With reference to their direction of action, how does a centripetal force differ from a centrifugal force ? (ii) State the Principle of conservation of energy. (iii) Name the form of energy which a body may possess even when it is not in motion. (3) (b) A coolie is pushing a box weighing 1500 N up an inclined plane 7.5 m long on to a platform, 2.5 m above the ground. (i) Calculate the mechanical advantage of the inclined plane. (ii) Calculate the effort applied by the coolie. (iii) In actual practice, the coolie needs to apply more effort than what is calculated. Give one reason why you think the coolie needs to apply more effort. (3) (c) A block and tackle system of pulley s a velocity ratio 4. (i) Draw a labelled diagram of the system indicating clearly the points of application and directions of a load and effort. (ii) What is the value of the mechanical advantage of the given pulley system if it is an ideal pulley system ? (4) Answer. (a) (i) With reference to action, the centripetal force is directed towards the centre of circular path and the centrifugal force is directed away from the centre of circular path, such that they are acting opposite to one another. (ii) Law of conservation of energy : Energy in a system cannot be created, nor it can be destroyed and the sum total of energy remains constant, no matter it can change its form. (iii) Potential energy. (b) (i) For a perfect machnine ; Mechanical advantage = Velocity ratio Distance through w hich effort acts 7.5 m = Distance through w hich load acts = 2.5 m = 3 (ii) Mechanical advantage = Effort = Load Effort \ 3 = 1500 N Effort Block and tackle system with velocity ratio 4 1500 N = 500 N. 3 (iii) Inclined plane is not a perfect machine. It offers certain amount of resistance to the load. Thus, in actual E practice coolie has to apply more effort. (c) (i) Load = 4T E= T \ V.R. = 4 Block and tackle system of pulley having V.R. = 4 (ii) Mechanical advantage will be equal to the number of pulleys engaged in a given pulley system. E E E E Load L Ph- 42 2013 Question 6 (a) Name the radiations : (i) that are used for photography at night. (ii) used for detection of fracture in bones. (ii) whose wavelength range is from 100 o A to 4000 o A (or 10 nm to 400 nm). (3) (b) (i) Can the absolute refractive index of a medium be less than one ? (ii) A coin placed at the bottom of a beaker appears to be raised by 4.0 cm. If the refractive index of water is 4/3, find the depth of the water in the beaker. (3) (c) An object AB is placed between 2F1 and F1 on the principal axis of a convex lens as shown in the diagram. Copy the diagram and using three rays starting from point A, obtain the image of the object formed by the lens. (4) Answer (a) (i) infrared radiation. (ii) X-rays. (iii) Ultraviolet radiation. (b) (i) No, absolute refractive index of a medium is always greater than 1, as speed of light in any medium is always less than that in vacuum. (ii) Let the real depth of water = x Apparent depth of water = (x 4) cm. Real depth 4 x Now, refractive index of water = Apparent depth 3 = x - 4 or (4x 16) = 3x \ Real depth = x = 16 cm (c) Question 7. (a) (i) What is the principle on which SONAR is based. (ii) An observer stands at a certain distance away from a cliff and produces a loud sound. He hears the echo of the sound after 1.8 s. Calculate the distance between the cliff and the observer if the velocity of sound in air is 340 ms 1. Ph- 43 2013 (b) A vibrating tuning fork is placed over the mouth of a burette filled with water. The tap of the burette is opened and the water level gradually starts falling. It is found that the sound from the tuning fork becomes very loud for a particular length of the water column. (i) Name the phenomenon taking place when this happens. (ii) Why does the sound become very loud for this length of the water column ? (3) (c) (i) What is meant by the terms (1) amplitude (2) frequency of a wave ? (ii) Explain why stringed musical instruments, like the guitar, are provided with a hollow box. (4) Answer (a) (i) Echo depth sounding Ultrasonic waves have the same speed as of audible sound but are not absorbed in the medium. So transmitter sends these waves receiver receives the waves back after striking vt the rigid obstacle so time taken is recorded. And we can calculate distance d = . 2 Velocity of sound time 340ms 1 1.8s = (ii) Distance between cliff and source of sound = 2 2 = 306 m (b) (i) The phenomenon is called resonance of sound . (ii) A some particular length of air column the natural frequency of air column corresponds the frequency of tuning fork. At this moment the sound waves reinforce to produce loud sound. (c) (i) The maximum displacement of vibrating particle about its mean position is called its amplitude.The number of waves which pass through a point in a medium in one second is called frequency. (ii) The air trapped in the hollow box starts vibrating with forced vibrations, thereby producing lounder sound. Question 8. (a) (i) It is observed that the temperature of the surrounding starts falling when the ice in a frozen lake starts melting. Give a reason for the observation. (ii) How is the heat capacity of the body related to its specific heat capacity ? (3) (b) (i) Why does a bottle of soft drink cool faster when surrounded by ice cubes than by ice cold water, both at 0o C ? (ii) A certain amount of heat Q will warm 1 g of material X by 3oC and 1 g of material Y by 4oC. Which material has a higher specific heat capacity. (c) A calorimeter of mass 50 g and specific heat capacity 0.42 J g 1 oC 1 contains some mass of water at 20oC. A metal piece of mass 20 g at 100 oC is dropped into the calorimeter. After stirring, the final temperature of the mixture is found to be 22oC. Find the mass of water used in the calorimeter. [specific heat capacity of the metal piece = 0.3 Jg 1 oC 1 ; specific heat capacity of water = 4.2 Jg 1 oC 1] (4) Answer (a) (i) Every kilogram of ice at 0oC on melting to form water at 0oC needs 336 103 J of heat energy as its specific latent heat is 336 103J. This heat energy is supplied by the surrounding of the lake, which in turn results in the fall in temperature. Ph- 44 2013 (ii) Specific heat capacity of a body = Heat capacity of the body Mass of the body (b) (i) Every gram of ice surrounding the soft drink extracts out 336 J of heat energy from it and the temperature of surrounding the soft drink remains at 0 oC. However, in case of cold water, it will extract out only 4.2 J of heat energy per gram. Furthermore, the temperature of surrounding water starts rising. Thus, soft-drink bottle cools better in case of ice. (ii) Material X has higher specific heat capacity compared to material Y. It is because for the mass amount of heat its temperature rises less than Y. (c) Data Substance Mass SHC Initial temperature Final temperature = 22 oC Calorimeter 50 g 0.42 Jg 1 oC 1 20oC q R = (22 20) = 2oC Cold water ? (x) 0.42 Jg 1 oC 1 20oC q R = (22 20) = 2oC Hot metal piece 20 g 0.3 Jg 1 oC 1 100 oC q F = (100 22) = 78oC Heat absorbed by cold water = mc q R = x 4.2 2 = 8.4x Heat absorbed by calorimeter = mc q R = 50 0.42 2 = 42 Total heat absorbed = 8.4x + 42. Heat given out by metal mc q F = 20 0.3 78 = 468. By the principle of calorimetry, Total heat absorbed = total heat lost 8.4x + 42 = 468 8.4x = 468 42 = 426 x = 426 = 50.7 g 8 .4 Question 9. (a) (i) State Ohm s law. (ii) A metal wire of resistance 6 W is stretched so that its length is increased to twice its original length. Calculate its new resistance. (3) (b) (i) An electrical gadget can give an electric shock to its user under certain circumstances. Mention any two of these circumstances. (ii) What preventive measure provided in a gadget can protect a person from an electric shock ? (c) The figure shows a circuit When the circuit is switched on, the ammeter reads 0.5 A. Ph- 45 2013 (i) Calculate the value of the unknown resistor R. (ii) Calculate the charge passing through the 3 W resistor in 120s. (4) (iii) Calculate the power dissipated in the 3 W resistor.. Answer (a) (i) Ohm s Law : It states, all physical conditions of a conductor remaining same, the current flowing through it is directly proportional to the potential difference at its ends. (ii) Let the original length be (l) and area of cross-section (a), such that its resistance is 6 W . Applying, R = K 1 Kl 6 = a a When the length 2l, its area of cross-section becomes ...(i) a . If R is the new resistance of 2 conductor then : R = K Kl 2l =4 a/2 a Dividing (ii) by (i) R =4 6 ....(ii) \ R = 24 W (b) (i) (1) The electrical gadget may be short circuited i.e., its live or neutral wire is touching its metallic body directly. (2) The hands of the user may be wet, such that water dripping from his hands makes contact with the live wire. (ii) The body of the electric gadget is connected to the earth terminal by means of earth wire. In case of short circuit a huge surge of current flows through the earth terminal. This in turn melts fuse in the live wire and hence the flow or current stops in the gadget. (c) (i) I = V R \ 0.5 = 6 R +3 \ 0.5 R + 1.5 = 6 0.5 R = 4.5 R = 9 W (ii) Charge Q = I t = 0.5 120 = 60 Coulombs (iii) Power dissipated in 3 W resistor = I2R = 0.5 0.5 3 = 0.75 W Question 10. (a) Name the three main parts of a Cathode Ray Tube. (b) (i) What is meant by Radioactivity ? (ii) What is meant by nuclear waste ? (iii) Suggest one effective way for the safe disposal of nuclear waste. (c) (i) Draw a simple labelled diagram of d.c. electric motor. (ii) What is the function of the split rings in a d.c. motor ? (iii) State one advantage of a.c. over d.c. Answer (a) (i) (1) electron gun (2) Deflecting plates (3) Fluorescent screen (b) (i) The phenomenon due to the nucleus of certain elements decays on its own, giving (3) (3) (4) out Ph- 46 2013 harmful radiations, such as a alpha particles, beta particles and gamma radiations is called radioactivity. (ii) The residual material left in the nuclear reactors after generating heat energy is called nuclear waste. The nuclear waste is radioactive and very harmful to the environment. (iii) The nuclear waste should be stored in stainless steel containers, lined from within with thick sheets of lead, so that no radioactive rays come out of it. The containers should be stored in safe and well guarded place, so that they do not fall in the hands of criminal elements. (c) (i) (ii) The split rings alter the direction of current in the coil after every half rotation. This in turn helps the coil to move in the same direction, i.e., clockwise or anticlockwise direction. (iii) The alternating current can be easily stepped up or down and can be transmitted over long distance cable wires. This is not possible in case of direct current. ICSE EXAMINATION QUESTION PAPER 2014 (SOLVED) Time : 2 hours 80 Marks Answers to this paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the Question Paper. The time given at the head of this paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. SECTION I (40 Marks) (Attempt all questions from this section) Question 1. (a) A force is applied on (i) a non-rigid body and (ii) a rigid body. How does the effect of the force differ in the above two cases? [2] (b) A metallic ball is hanging by a string from a fixed support. Draw a neat labelled diagram showing the forces acting on the ball and the string. [2] (c) (i) What is the weight of a body placed at the centre of the earth? (ii) What is the principle of an ideal machine? [2] (d) Is it possible to have an accelerated motion with a constant speed? Explain. [2] (e) (i) When does a force do work? (ii) What is the work done by the moon when it revolves around the earth? [2] Answer. (a) (i) When a force applied on a non-rigid body, it changes the interspacing between its constituent particles and therefore causes a change in its dimensions and can also produce motion in it. (ii) When a force is applied on a rigid body, it does not change the interspacing between its constituent particles and therefore it does not change the dimensions of the object but causes only the motion in it. Support (b) T T Tension in the string mg Weight of the ball mg (c) (i) The weight of a body placed at the centre of the earth is zero because value of g = 0 at the center of the earth. (ii) An ideal machine is that in which there is no dissipation of energy in any manner. \ Principle of an ideal machine = work done by a machine = work done on the machine / work output = work input Ph- 47 2014 Ph- 48 2014 (d) Yes. The velocity of particle in circular motion is variable or the circular motion is accelerated even though the speed of particle is uniform. (e) (i) Work is said to be done only when the force applied on a body makes the body moves i.e., there is displacement of the body. (ii) The work done by the moon when it revolves around the earth is zero. Question 2. (a) Calculate the change in the Kinetic energy of a moving body if its velocity is reduced to 1/3rd of the initial velocity. [2] (b) State the energy changes in the following devices while in use : (i) A loud speaker. (ii) A glowing electric bulb. [2] (c) (i) What is nuclear energy? (ii) Name the process used for producing electricity using nuclear energy. [2] (d) State one important advantage and disadvantage each of using nuclear energy for producing electricity. [2] (e) (i) The conversion of part of the energy into an undesirable form is called ............. . (ii) For a given height h, ............. the length 1 of the inclined plane, lesser will be the effort required. [2] Answer. (a) Initial K.E = 1 mv2 2 1 1 Change in velocity = \ Final K.E. = K.E2 = 1 of initial velocity 3 1 1 v mv2 = m 2 2 3 = v2 1 m 9 2 = 1 9 2 1 2 2 mv 1 th of initial K.E. 9 (b) (i) Electrical energy converted to sound energy. (ii) Electrical energy converted to heat energy and to light energy. (c) (i) In nuclear fission and fusion there is a loss in mass due to loss in mass energy released. The energy so released is called the nuclear energy. = Ph- 49 2014 (ii) Nuclear fission. (d) Advantage : A very small amount of nuclear fuel can produce a tremendous amount of energy. Disadvantage : Very harmful nuclear radiations are produced in the process which are highly energetic and penetrating. (e) (i) Dissipation of energy. (ii) More. Question 3. (a) Draw the diagram given below and clearly show the path taken by the emergent ray. [2] 45 (b) (i) What is consumed using different electrical appliances, for which electricity bills paid? (ii) Name a common device that uses electromagnets. (c) (i) A ray of light passes from water to air. How does the speed of light change? (ii) Which colour of light travels fastest in any medium except air? (d) Name the factors affecting the critical angle for the pair of media. (e) (i) Name a prism required for obtaining a spectrum of Ultraviolet light. (ii) Name the radiations which can be detected by a thermopile. Answer. (a) are [2] [2] [2] [2] P 45 Q 45 (b) (c) Correct path of the refracted ray shown Correct path of emergent ray shown (i) Electrical energy. (ii) Electrical bell (Door Bell) / microphone / Electric motor (i) Speed of light increases. (ii) Red colour of light travels fastest in any medium except air. Ph- 50 2014 (d) Factors affecting the critical angle for the pair of media are : (i) Wavelength of light (ii) Effect of temperature of the medium (iii) Refractive index of the pair of media. (e) (i) Quartz prism. (ii) Infrared radiations can be detected by thermopile. Question 4. (a) Why is the colour red used as a sign of danger? [2] (b) (i) What are mechanical waves? (ii) Name one property of waves that do no change when the wave passes from one medium to another. [2] (c) Find the equivalent resistance between points A and B. 3W 3W A [2] 4W 5W 6W B 3W (d) 50 g of metal piece at 27 C requires 2400 J of heat energy so as to attain a temperature of 327 C. Calculate the specific heat capacity of the metal. [2] (e) An electron emitter must have ............. work function and ............. melting point. [2] Answer. (a) Since the wavelength of red light is maximum in the visible light, the light of red colour is scattered least by the air molecules of the atmosphere and therefore it can reach to a longer distance and can be seen easily from farthest distance. (b) (i) The waves which require a medium for their propagation are called elastic or mechanical waves. These waves travel in the medium though the vibrations of the medium particles about their mean positions. (ii) Frequency. (c) 1 1 1 1 3 = + + = =1 R1 3 3 3 3 R1 = 1W R2 = 5W 1 1 1 3+ 2 5 = + = = R3 4 6 12 12 Ph- 51 R3 = 2014 12 = 2.4W 5 Total R = R1 + R2 + R3 = 1 + 5 + 2.4 = 8.4W. (d) Given : m = 50g; Dt = 327 C 27 C = 300 C, Q = 2400 J. Now, Q = mC Dt 2400 = 50 C 300 C= 2400 = 0.16 J/g C 50 300 (e) An electron emitter must have low work function and high melting point. SECTION II (40 Marks) (Attempt any four questions from this Section) Question 5. (a) (i) A man having a box on his head, climbs up a slope and another man having an identical box walks the same distance on a levelled road. Who does more work against the force of gravity and why? (ii) Two forces each of 5N act vertically upwards and downwards respectively on the two ends of a uniform metre rule which is placed at its mid-point as shown in the diagram. Determine the magnitude of the resultant moment of these forces about the midpoint. [4] 5N 50 cm 5N (b) (i) A body is thrown vertically upwards. Its velocity keeps on decreasing. What happens to its kinetic energy as its velocity becomes zero? (ii) Draw a diagram to show how a single pulley can be used so as to have its ideal M.A. = 2. [3] (c) Derive a relationship between mechanical advantages, velocity ratio and efficiency of a machine. [3] Answer. (a) (i) Man climbs up a slope does more work against the force of graving whereas the work done by the man walking on a levelled road is zero because displacement is normal to the force of gravity. Ph- 52 2014 (ii) F1 = F2 = 5N, d1 = d2 = 50 cm = 0.5 m Torque t = F d t1 = F1 d1 = = 5N 0.5 m = 2.5 N m (Anti-clockwise) t2 = F2 d2 = 5N 0.5 m = 2.5 N m (Anti-clockwise) The resultant moment of force = t1 + t2 = 2.5 + 2.5 = 5N m in Anti clockwise direction. (b) (i) When a body thrown vertically upward its velocity continuously decreases, kinetic energy also decrease and potential energy increases due to increase in height. \ K.E. completely changes to P.E. (ii) Single Movable Pulley. Rigid Support E T T=E Axle Frame Single movable Pulley L (c) Let a machine overcome a load L by the application of an effort E. In time t, let the displacement of effort be dE and the displacement of load be dL. Work input = Effort displacement of effort = E dE Work output = Load displacement of load = L dL Efficiency = Work output Work input = L dL dL L = E dE dE E = 1 L dE / dL E But L = M.A. E Ph- 53 and 2014 dE = V.R. dL \ Efficiency h = M.A. or M.A. = V.R. h V.R. Thus, the mechanical advantage of a machine is equal to the product of its efficiency and velocity ratio. Question 6. (a) (i) Light passes through a rectangular glass slab and through a triangular glass prism. In what way does the direction of the two emergent beams differ and why? (ii) Ranbir claims to have obtained an image twice the size of the object with a concave lens. Is he correct? Give a reason for your answer. [4] (b) A lens forms an erect, magnified and virtual image of an object. (i) Name the lens. (ii) Draw a labelled ray diagram to show the image formation. (c) (i) [3] Define the power of a lens. (ii) The lens mentioned in 6(b) above is of focal length 25 cm. Calculate the power of the lens. [3] Answer. (a) (i) In a rectangular glass slab, the emergent ray is parallel to the incident ray but they are not along the same line whereas in a prism the emergent ray is not parallel to incident ray. Because in a glass block the two surfaces at which refraction occurs is parallel to each other. (ii) No. By the concave lens only diminished images are obtained. (b) (i) Convex lens. (ii) Object drawn b/w the optical center and the principle focus. B B 2F2 2F1 A F1 A O F2 Convex lens (c) (i) The power of a lens is a measure of deviation produced by it in the path of rays refracted through it. Ph- 54 2014 (ii) Power of lens (in D) = 1 Focal length (in metre) = 100 Focal length (in centimetre) = 100 = 4D. 25 Question 7. (a) The adjacent diagram shows three different modes of vibrations P, Q and R of the same string. (i) Which vibrations will produce a louder sound and why? (ii) The sound of which string will have maximum shrillness? (iii) State the ratio of wavelengths of P and R. [4] P Q R (b) A type of electromagnetic wave has wavelength 50 A . (i) (ii) (iii) (c) (i) (ii) Answer. (a) (i) (ii) (iii) (b) (i) (iii) Name the wave. What is the speed of the wave in vacuum? State one use of this type of wave. [3] State one important property of waves used for echo depth sounding. A radar sends a signal to an aircraft at a distance of 30 km away and receives it back after 2 10 4 second. What is the speed of the signal? [4] R will produce louder sound because its amplitude is more than P and Q. The sound of P string will have maximum shrillness. The ratio of wavelength of P and R is 1 : 3. X-Rays. (ii) 3 108 m/s. X-Rays are used for detection of fracture in bones. Ph- 55 2014 (c) (i) The ultrasonic waves travel undeviated through long distances and they can be confined to a narrow beam. (ii) Distance of aircraft = 30 km = 30 1000 m = 30,000 m Total distance = 2 30,000 = 60,000 m Time taken = 2 10 4 second Hence, Speed of sound V = = distance travelled (2d ) time taken (t ) 60,000 = 30,000 104 m/s 2 10 - 4 = 3 108 m/s. Question 8. (a) Two resistors of 4W and 6W are connected in parallel to a cell to draw 0.5 A current from the cell. (i) Draw a labelled circuit diagram showing the above arrangement. (ii) Calculate the current in each resistor. [3] (b) (i) What is an Ohmic resistor? (ii) Two copper wires are of the same length, but one is thicker than the other. (1) Which wire will have more resistance? (2) Which wire will have more specific resistance? [3] (c) (i) Two sets A and B, of the three bulbs each, are glowing in two separate rooms. When one of the bulbs in set A is fused, the other two bulbs, alos cease to glow. But in set B, when one bulb fuses, the other two bulbs continue to glow. Explain why this phenomenon occurs. (ii) Why do we prefer arrangement of Set B for house circuiting? [3] Answer. (a) (i) 4W 6W r = 0.6 W 0.5A 1.5 V (ii) Let current through 4W resistance is i then current through 6W resistance is (0.5 i) \ i 4 = (0.5 i) 6 4i = 3 6i Ph- 56 2014 4i + 6i = 3 10i = 3 i = 0.3 A \ Current through 4W resistance = 0.3 A and current through 6W resistance = 0.5 0.3 = 0.2 A (b) (i) Ohmic Resistors : The conductors which obey Ohm s law are called the Ohmic resistors or linear resistances. For such resistors, a graph plotted for the potential difference V against current I is a straight line. (ii) (1) Thin wire will have more resistance because the resistance is inversely proportional to area of cross-section. (2) Specific resistance of both wire is same because specific resistance depends upon the nature of the medium which is the same (copper) in both cases. (c) (i) The bulbs of set A are connected in series. Therefore when one bulb fuse the current stop flowing. Whereas the bulbs of set B are connected in parallel. When one bulb fuse then the current flows through the other bulb. (ii) Set B prefer parallel combination because in it potential difference remains same. Question 9. (a) Heat energy is supplied at a constant rate to 100g of ice at 0 C. The ice is converted into water at 0 C in 2 minutes. How much time will be required to raise the temperature of water from 0 C to 20 C? [Given : sp. heat capacity of water = 4.2 J g 1 C 1 , sp. latent heat of ice = 336 J g 1 ]. [4] 1 1 (b) Specific heat capacity of substance A is 3.8 J g K whereas the Specific heat capacity of substance B is 0.4 J g 1 K 1 . (i) Which of the two is a good conductor of heat? (ii) How is one led to the above conclusion? (iii) If substances A and B are liquids then which one would be more useful in car radiators? [3] (c) (i) State any two measures to minimize the impact of global warming. (ii) What is the Greenhouse effect? [3] Answer. (a) m = 100g, t = 2 minutes = 2 60 sec. Heat energy taken by ice at 0 C to convert to water at 0 C. Q = mL = 100 336 = 33600 J \ P= Q 33600 = = 280 J/S t 2 60 The heat energy required to convert water at 0 C to 20 C. Q = mC Dt = 100 4.2 20 = 8400 J Q=P t Ph- 57 2014 8400 = 280 t t= 8400 280 t = 30 sec. = 0.5 min. (b) (i) Substance B is a good conductor of heat. (ii) Because specific capacity of B is less then that of A. [lower the specific heat capacity, better the conducting power] (iii) Substance A is more useful in car radiator. (c) (i) Two measures to minimize the impact of global warming are : (1) Technological measures (2) Economic measures (ii) The green house effect is the phenomenon in which infrared radiations of long wavelength given out from the surface of the earth are absorbed by its atmospheric gases to keep the environment warm at the earth s surface and the lower atmosphere. Question 10. (a) (i) Name two factors on which the magnitude of an induced e.m.f. in the secondary coil depends. (ii) In the following diagram an arrow shows the motion of the coil towards the bar magnet. (1) State in which direction the current flows, A to B or B to A? (2) Name the law used to come to the conclusion. Magnet S N A B (b) A nucleus 11 Na 24 emits a beta particle to change into Magnesium (Mg) (i) Write the symbolic equation for the process. (ii) What are numbers 24 and 11 called? (iii) What is the general name of (c) In a (i) (ii) (iii) Answer. (a) (i) 24 12 Mg with respect to 24 ? 11 Na cathode ray tube state : The purpose of covering cathode by thorium and carbon. The purpose of the fluorescent screen. How is it possible to increase the rate of emission of electrons. [3] [3] The magnitude of induced e.m.f. in the secondary coil depends on the following two factors : Ph- 58 2014 (1) The change in the magnetic flux, and (2) The time in which the magnetic flux changes. (ii) (1) A to B (2) Lenz s law. 24 + 0 (b) (i) 11 NA24 Mg e 12 1 (ii) The number 24 is atomic mass number (number of protons and neutrons) and 11 is atomic number. (iii) They are isobars. (c) (i) The purpose of covering cathode by thorium and carbon is to decrease the work function or to emit electrons at lower temperature. (ii) To convert electrical signal into a visual signal. (iii) By increasing the temperature of cathode or By increasing the filament current, the rate of emission of electrons from the cathode will increase. Ph- 73 2015 Ans. (i) The emission of electrons from a metal surface when heat energy is imparted to it is called thermionic emission. (ii) Work function of a metal is expressed in terms of electron volt (eV) where 1eV = 1.6 10 19J. (b) [5] (i) Complete the diagram as given below by drawing the deflection of radioactive radiations in an electric filed. (ii) State any two precautions to be taken while handling radioactive substances. Ans. (i) Deflection of radioactive radiations a, b and g in an electric field is as shown below: Lead box Radioactive substance (ii) The two safety precautions to be taken while handling radioactive substances are (any two): i. Radioactive substances should be kept in thick lead containers with a very narrow opening so as to restrict the radiations coming out from other directions. ii. Radioactive materials should be handled with long lead tongs. ICSE QUESTION PAPER-2016 (SOLVED) PHYSICS SCIENCE Paper 3 (One hour and a half) Answers to this Paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the Question Paper, The time given at the head of this Paper is the time alloted for writing the answers. Attempt all questions from Section I and any four questions from Section II. The intended marks of questions or parts of questions are given in brackets [ ]. SECTION I (40 Marks) Attempt all questions from this Section Question 1 (a) (i) Give an example of a non contact force which is always of attractive nature. (ii) How does the magnitude of this non contact force on the two bodies depend on the distance of separation between them? [2] (b) A boy weighing 40 kgf climbs up a stair of 30 steps each 20 cm high in 4 minutes and a girl weighing 30 kgf does the same in 3 minutes. Compare: (i) The work done by them. (ii) The power developed by them. [2] (c) With reference to the terms Mechanical Advantage, Velocity Ratio and efficiency of a machine, name and define the term that will not change for machine of a given design. [2] (d) Calculate the mass of ice required to lower the temperature of 300 g of water 40 oC to water at 0oC. [2] o (Specific latent heat of ice = 336 J/g, Specific heat capacity of water = 4.2J/g C) (e) What do you understand by the following statements: (i) The heat capacity of the body is 60JK-1. (ii) The specific heat capacity of lead is 130 Jkg-1K-1. [2] Answer: (a) (i) The example of non-contact force is gravitational force. It is always attractive in nature. (ii) The magnitude of non-contact forces acting on two bodies depends on the distance of separation between them. The magnitude of force decreases with an increase in separation and increases as the separation decreases. It varies inversely as the square of the distance of separation. (b) Given: Force of gravity of the boy, Fb = 40 kgf Time taken by him, tb = 4 minutes = 4 60 s = 240 s Force of gravity of the girl, Fg = 30 kgf Time taken by her, tg = 3 minutes = 3 60 s = 180 s Ph- 75 2016 Ph- 76 2016 Distance covered by both in 30 steps is D = 30 20 = 600 cm While climbing, both have to do work against the force of gravity. (i) Work done by the boy in climbing the stairs: Wb = F D = 40 kgf 600 cm Wb = 24000 J Work done by the girl in climbing the stairs: Wg = F D = 30 kgf 600 cm Wg = 18000 J \ 24000J Wb = Wg 18000J Wb 4 = Wg 3 (ii) Power developed = Work done Time taken For the boy : Power Developed = 24000 J = 100W 240 s For the girl : Power Developed = 18000 J = 100W 180 s Thus, power developed by them is 1 : 1 Or (i) Work done by the boy = 40 10 6 = 2400 J Work done by the girl = 30 10 6 = 9800 J \ Ratio = 2400 : 1800 = 4 : 3 (ii) Power of boy = 2400 = 10 watt 4 60 Power of girl = 2400 = 10 watt 3 60 \ Ratio = 1 : 1 (c) Velocity ratio. It is the ratio of the velocity of effort to the velocity of load. Ph- 77 2016 VE V.R. = V . L Velocity ratio does not change. (d) Let m be the mass of the ice to be added. Heat energy required to melt to lower the temperature is = mL = m 336 Heat energy imparted by the water in fall of its temperature from 40 C to 0 C = mass of the water specific heat capacity fall in temperature. = 300 4.2 40 C If there is no loss of heat, m 336 J/g = 300 g 4.2 J/g C 40 C 300 4.2 40 336 m = 150g (e) (i) Heat capacity is the amount of heat required to raise the temperature of a body by 1 C or 1 K. Thus, 60 JK 1 of energy is required to raise the temperature of the given body by 1 K. (ii) Specific heat capacity is the amount of heat energy required to raise the temperature of unit mass of a substance through 1 C or 1K. Thus, 130 JKg 1 K 1 of heat energy required to raise the temperature of unit mass of lead through 1 K. Question 2 (a) State two factors upon which the heat absorbed by a body depends. [2] (b) A boy uses blue colour of light to find the refractive index of glass. He then repeats the experiment using red colour of light. Will the refractive index be the same or different in the two cases? Give a reason to support your answer. [2] m= A (c) Copy the diagram given below and complete the path of the light ray till it emerges out of the prism. The critical angle of glass is 42 . In your diagram mark the angles wherever necessary. [2] 60 P (d) State the dependence of angle of deviation: Q (i) On the refractive index of the material of the prism. 60 60 (ii) On the wavelength of light [2] B C (e) The ratio of amplitude of two waves is 3:4. What is the ratio of their: (i) loudness? (ii) Frequencies? [2] Answer : (a) Heat absorbed by a body depends on the mass of the body, change in temperature of the body and the specific heat capacity of the body. (b) The refractive index will be different in both cases. Refractive index of glass is different for different colours. The speed of blue light is less than the speed of red light. So, the wavelength of blue light is less than that of red light. Thus, red light would deviate less than blue light because of difference in wavelength. Ph- 78 2016 (c) The diagram is as shown : (d) (i) Angle of deviation is directly proportional to the refractive index of the material of prism. For a given angle of incidence, the prism with higher refractive index produces a greater deviation than the prism which has a lower refractive index. Thus, the angle of deviation increases with an increase in the refractive index of the medium. (ii) Angle of deviation is inversely propotional to the wavelength of the light used. The angle of deviation decreases with an increase in the wavelength of light. Thus, a prism deviates violet light the most and red light the least. (e) (i) Let a1 and a2 be the amplitudes and I1 and I2 be the intensities of the two waves. I1 a12 32 I = 2 = 2 a2 4 2 I1 9 I = 16 2 I1 : I1 = 9 : 16 (ii) Frequency is the number of waves formed per second. It only depends on time period. Thus, the ratio of their frequencies is 1:1. Question 3 (a) State two ways by which the frequency of transverse vibrations of a stretch string can be increased. [2] (b) What is meant by noise pollution? Name one source of sound causing noise pollution. [2] (c) The V-I graph for a series combination and for a parallel combination of two resistors is shown in the figure below. Which of the two A or B. represents the parallel combination? Give reasons for your answer. [2] Ph- 79 2016 (d) A music system draws a current of 400 mA when connected to a 12 V battery. [2] (i) What is the resistance of the music system? (ii) The music system if left playing for several hours and finally the battery voltage drops to 320 mA and the music system stops playing when the current. (e) Calculate the quantity of heat produced in a 20 W resistor carrying 2.5 A current in 5 minutes. [2] Answer : (a) The frequency of transverse vibration is given by f= 1 2l T r 2d 1 T 2l m where l = length of the vibrating string T = tension in the string m = mass per unit length of the string Therefore, the frequency of transverse vibration of a stretched string can be increased by decreasing the length of the string decreasing the mass per unit length of the string increasing the tension T in the string The disturbance produced in the environment because of undesirable loud and harsh sound of level more than 120 dB from the various sources such as a loudspeaker and moving vehicles is called noise pollution. Ex : Honking of vehicles in traffic jams. For the same change in I, change in V is less for the straight line A than for the straight line B (i.e. the straight line A is less steep than B). The straight line A represents small resistance, while the straight line B represents more resistance. The equivalent resistance is less in a parallel combination than in a series combination. So, line A represents a parallel combination. or f = (i) (ii) (iii) (b) (c) (d) (i) Given : I = 400 mA = 400 10 3 A V = 12 V V = IR V 12V R= I = 400 10-3A R = 30 (ii) Current drops to I = 320 mA = 320 10 3 A The music stops playing at V = IR = 320 10 3 30 V = 9.6 V Ph- 80 2016 (e) Given : R = 20 , I = 2.5 A t = 5 minutes = 5 60 = 300 s Quantity of heat produced is given as H = I2Rt = (2.5)2 20 300 H = 37500 J Question 4 (a) State the characteristics required of a good thermion emitter. [2] A 222 (b) An element ZS decays to 85R after emitting 2 a particles and 1 b particle. Find the atomic number and atomic mass of the element S. [2] (c) A radioactive substance is oxidized. Will there be any change in the nature of its radioactivity? Give a reason for your answer. [2] (d) State the characteristics required in a material to be used as an effective fuse wire. [2] (e) Which coil of a step up transformer is made thicker and why? [2] Answer : (a) Two characteristic which a thermionic emitter should possess are 1. The work function of the substance should be low such that the electrons are emitted from it even when it is not heated to a very high temperature. 2. The melting point of the substance should be quite high so that it may not melt when it is heated to the temperature required for thermionic emission. (b) The decay will follow the following sequence A 4 A 8 A 8 SA z 2 P z 4 Q z 3 R Therefore, we have Z 3 = 85 or Z = 85 + 3 = 88 And A 8 = 222 or A = 222 + 8 = 230 Z = 88, A = 230 (c) No, radioactivity is not affected by any physical process. (d) The material should have high resistivity and low melting point. (e) Primary coil, as it has lesser number of turns. Z SECTION II (40 Marks) (Attempt any four questions from this Section) Question 5 (a) A stone of mass m is rotated in a circular path with a uniform speed by tying a strong string with the help of your hand. Answer the following questions : (3) (i) Is the stone moving with a uniform or variable speed ? (ii) Is the stone moving with a uniform acceleration ? In which direction does the acceleration act? (iii) What kind of force acts on the hand and state its direction ? (b) From the diagram given below. answer the question that follow : (3) Ph- 81 2016 B T T A T C L (i) What kind of pulleys are A and B ? (ii) State the purpose of pulley B. (iii) What effort has to be applied at C just raise the load L = 20 kgf ? (Neglect the weight of pulley A and friction) (c) (i) An effort is applied on the bigger wheel of a gear having 32 teeth. It is used to turn a wheel of 8 teeth. Where it is used. (ii) A pulley system has three pulleys. A load of 120 N is overcome by applying an effort of 50 N. Calculate the Mechanical Advantage and Efficiency of this system. (4) Answer : (a) (i) The stone is moving with uniform speed as given in the question. (ii) Although the stone is rotating with uniform speed, its direction keeps on acceleration. The direction of acceleration is towards the centre of the circular path. (iii) Centrifugal force acting radially outwards. (b) (i) The pulley A is a single movable pulley and B is a single fixed pulley. (ii) So as to apply the effort in a convinient direction that is vertically downwards. (iii) Distance moved by load dL = x / 2. Distance moved by the effort dE = x Load = 20 kgf, Effort = ? Now, Load dL = Effort dE 20 x / 2 = Effort x or Effort = 10 kgf (c) (i) The number of teeth in the driving wheel is nB = 32 and that in the driven wheel is nA = 8. Hence, this system is used to obtain gain in speed. n B 32 Gain in speed = n = 8 =4 A (ii) Load = 120 N; E = 50 N; n = 3 Mechanical advantage of pulley system is Ph- 82 2016 L 120 = = 2.4 E 50 The efficiency of the system is M.A. = = M.A 2.4 2.4 = = =0.8=80% V.A n 3 Question 6. (a) (i) What is the principle of method of mixtures ? (3) (ii) What is the other name given to it ? (iii) Name the law on which the principle is based (b) Some ice is heated at a constant rate, and its temperature is recorded after every few seconds, till steam is formed at 100 C. Draw a temperature time graph to represent the change. Label the two phase changes in your graph. (3) (c) A copper vessel of mass 100 g contains 150 g of water at 50 C. How much ice is needed to cool it to 5 C ? (4) Given : Specific heat capacity of copper = 0.4 Jg 1 C 1 Specific heat capacity of water = 4.2 Jg 1 C 1 Specific latent heat of fusion ice = 336 Jg 1 Answer : (a) (i) The principle of method of mixture says that the heat lost by a hot body is equal to the heat gained by a cold body provided no heat is last to the surroundings. (ii) The other name given to the principle of mixture is the principle of calorimetry. (iii) The principle of mixture is based on the law of conservation of energy. (b) The figure for phase change is shown below : Vaporization 100 C temp 0 C Melting time Correct graph (Axes and Shape) Melting marked Vaporization marked (c) Heat energy lost by the vessel and water contained in it in cooling the water from 50 C to 5 C is used in heating ice to melt it and then to raise its temperature from 0 C to 5 C. Now, heat energy lost by the copper vessel is Ph- 83 2016 QC = mCCC t = 100 0.4 (50 5) = 100 0.4 45 QC = 1800 J Similarly, heat energy lost by water is = 150 4.2 45 QW = mWCW t = 150 4.2 (50 5) QW = 28350 J Hence, the total heat energy lost is QL = 1800 + 28350 = 30150 J Let m g of ice be used to cool water. So, heat gained by ice is QI = mLice + mcW t QI = 336 m + m 4.2 5 = 336m + 21m = 357 J Therefore, from the principle of calorimetry, the mass of ice is QL = Q I 357m = 30150 30150 = 84.45 g 357 Question 7. (a) (3) (i) Write a relationship between angle of incidence and angle of refractions for a given pair of media. (ii) When a ray of light enters from one medium to another having different optical densities it bends. Why does this pehnomenon occur ? (iii) Write one conditions where it does not bend when entering a medium of different optical density. (b) A lens produces a virtual image between the object and the lens. (3) (i) Name the lens. (ii) Draw a ray diagram to show the formation of this image. (c) What do you understand by the term Scattering of light ? Which colour of white light is scattered the least and why ? (4) Answer : (a) (i) The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for m= a given pair of media called the refractive index = sini = sin r (ii) When a ray of light enters from one medium to another with different optical densities, it bends because there is a change in the speed of light in the two medium. (iii) A ray of light passing from one medium to another does not bend when incident normally at the surface of the second medium. (b) (i) The image formed by the lens is virtual and between the object and the lens. Hence, the lens used is a concave lens. (ii) The following image is of formation of the above image : Ph- 84 2016 B B1 2F2 A F2 A1 O (c) Scattering is the process of absorption and then re-emission of light energy without the change in the wavelength. The red colour of the white light is scattered the least because scattering of light depends inversely upon the four power of wavelength. As red colour has the maximum wavelength in the visible region, therefore, it scattered the least. Question 8. (a) (3) (i) Name the waves used for echo depth sounding. (ii) Give one reason for their use for the above purpose. (iii) Why are the waves mentioned by you not audible to us ? (b) (3) (i) What is an echo (ii) State two conditions for an echo to take place. (c) (i) Name the phenomenon involved in tuning a radio set to a particular station. (ii) Define the phenomenon named by you in part (i) above. (iii) What do you understand by loudness of sound ? (iv) In which units is the loudness of sound measured ? Answer : (a) (i) The waves used for echo depth sounding are ultrasonic waves. (ii) Ultrasonic waves are used for echo depth ranging because they can travel undeviated through a long distance. (iii) Ultrasonic waves have frequency larger than 20000 Hz. Hence, these waves are not audible to us as the audible range for the human ear is 20 Hz to 20000 Hz. (b) (i) The sound heard after reflection from a distant obstacle after the original sound has ceased is called an echo. (ii) The conditions for an echo to take place are Ph- 85 2016 a. The minimum distance between the source of sound and the reflector in air must be at least present 16 to 18 m. b. The size of the reflector must be large enough as compared to the wavelength of sound wave. (c) (i) The phenomenon involved in tuning a radio set to a particular station is called resonance. (ii) Resonance : When the frequency of an externally applied periodic force on a body is equal to its natural frequency, the body readily begins to vibrate with an increased amplitude. This phenomenon is known as resonance. (iii) Loudness is the property by virtue of which a loud sound can be distinguished from a faint one, both having the same pitch and quality. (iv) The loudness of sound is measured in phon / db / bel. Question 9. (a) (3) (i) Which particles are responsible for current in conductors ? (ii) To which wire of a cable in a power circuit should the metal case of a geyser be connected ? (b) (3) (i) Name the transformer used in the power transmitting station of a power plant. (ii) What type of current is transmitted from the power station ? 12 V (iii) At what voltage is this current available to our household ? 2W (c) A battery of emf 12 V and internal resistance 2 W is connected with two resistors A and B of resistance 4 W and 6 W respectively joined in series. (4) Find : A B (i) Current in the circuit 4W 6W (ii) The terminal voltage of the cell. (iii) The potential difference across 6 W Resistor. (iv) Electrical energy spent per minute in 4 W resistor. Answer : (a) (i) Electrons are responsible for current in conductors. (ii) The metal case of a geyser should be connected to the Earth wire. (iii) The fuse should always be connected to the live wire. (b) (i) A step-up transformer is used in the power transmitting station of a power plant. (ii) An alternating current is transmitted from the power station. (iii) The current is available to our household at a voltage of 220 V. (c) E = 12 V ; r1 = 2 W; RA = 4 W; RB = 6 W (i) The current in the circuit is E E = I= R total R1 + R A + R B Ph- 86 2016 12 I = 2 + 4 + 6 = 1A (ii) The terminal voltage of the cell is T.V. = IR T.V. = 1 (6 + 4) T.V. = 10 V (iii) The potential difference across the 6 resistor is VB = IRB VB = 1 6 = 6 V (iv) The electrical energy spent per minute (= 60s) is W = I2Rt W = 12 4 60 = 240 J Question 10. (a) Arrange , , and rays in ascending order with respect to their (i) Penetrating power. (ii) Ionising power. (iii) Biological effect. (b) (i) In a cathode ray tube what is the function of anode ? (ii) State the energy conversion taking place in a cathode ray tube. (iii) Write one use of cathode ray tube. (c) (3) (3) (3) (i) Represent the change in the nucleus of a radioactive element when a particle is emitted. (ii) What is the name given to elements with same mass number and different atomic number. (iii) Under which conditions does the nucleus of an atom tend to radioactive ? Answer : (a) (i) Penetrating power : < < (ii) Ionising power : < < (iii) Biological effect = < < (b) (i) In a cathode ray tube, the anode accelerates the electrons and also focuses them in a fine energetic beam. (ii) In a cathode ray tube, electrical energy is converted into heat and than light energy. (iii) A cathode ray tube is used to investigate the wave form of an unknown alternating potential by applying it on the Y-plates and a known periodic time-based potential on the X-plates or picture tube of T.V. Ph- 87 2016 (c) (i) In an unstable nucleus, the neutron is changed into a proton by emitting a beta particle. This is represented as 0 1 1 0 n 1p + 1 e (proton) ( -particle) (neutron) (ii) (iii) Elements with the same mass number but different atomic numbers are called isobars. The nucleus of an atom tends to be radioactive when nucleus has more mass nucleus has excess energy neutrons proton ratio becomes more than 1.3 to 1.5. ICSE EXAMINATION QUESTION PAPER 2017 (SOLVED) SCIENCE Paper I (PHYSICS) (One hour and a half hours) Answers to this paper must be written on the paper provided separately. You will NOT be allowed to write during the first 15 minutes. This time is to be spent in reading the question paper. The time given at the head of this paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. SECTION I (40 Marks) (Attempt all questions from this Section) Question 1. (a) A brass ball is hanging from a stiff cotton thread. Draw a neat labelled diagram showing the forces acting on the brass ball and the cotton thread. (2) (b) The distance between two bodies is doubled. How is the magnitude of gravitational force between them affected? (2) (c) Why is a jack screw provided with a long arm? (2) (d) If the power of a motor be 100 kW, at what speed can it raise a load of 50,000 N? (2) (e) Which class of level will always have MA > 1 and why? (2) Answer 1. (a) Support Tension (T) Weight, (W) (b) The magnitude of gravitational force between two bodies is inversely proportional to the square of the distance between them. G.F. \ (c) (d) \ \ 1 r2 As the distance is doubled, the force will become one fourth of the initial force. Increase in torque arm, increases the moment of force, so lesser effort is required for turming P = 100kW P = 100 1000W, F = 50000N Power = Force Velocity Ph- 88 2017 Ph- 89 2017 \ 100000 = 50000 V \ V = 2 ms 1 (e) Class II lever. Mechanical advantage = Effort arm Load arm In a class II lever, the effort arm is always longer than the load arm, hence its MA > 1. Question 2. (a) Define heat capacity and state its SI unit. (b) Why is the base of a cooking pan generally made thick? (2) (2) (c) A solid of mass 50 g at 150 C is placed in 100 g of water at 11 C, when the final temperature recorded is 20 C. Find the specific heat capacity of the solid. (Specific heat capacity of water = 4.2 J/g C) (d) How is the refractive index of a material related to : (i) real and apparent depth? (ii) velocity of light in vacuum or air and the velocity of light in a given medium? (e) State the conditions required for total internal reflection of light to take place. (2) (2) Answer 2. (a) Heat capacity of a body is the heat energy required to raise the temperature of the body by 1 C. Its S.I. unit is Jk 1. (b) The base is thick hence the mass of the base is more. This increases the heat capacity which enables the pan to hold a large amount of heat energy at a low temperature. The food is cooked properly and remains warm for a long time. (c) Heat lost by solid = Heat gained by water (MCDt)Solid = (MCDt)Water \ 50 C (150 20) = 100 4.2 (20 11) C= 100 4.2 9 50 130 \ C = 0.582 Jg 1 C 1 (d) (i) Refractive Index = (ii) Refractive Index = Real depth Apparent depth Velocity of light in air or vacuum Velocity of light in given medium (e) (i) The ray of light must travel from denser medium to rarer medium. (ii) The angle of incidence should be greater than the critical angle. Ph- 90 2017 Question 3. (a) Draw a ray diagram to show the refraction of a monochromatic ray through a prism when it suffers minimum deviation. (2) (b) The human ear can detect continuous sounds in the frequency range from 20 Hz to 20,000 Hz. Assuming that the speed of sound in air is 330 ms 1 for all frequencies, calculate the wavelengths corresponding to the given extreme frequencies of the audible range. (2) (c) An enemy plane is at a distance of 300 km from a radar. In how much time will the radar be able to detect the plane? Take velocity of radiowaves as 3 108 ms 1. (2) (d) How is the frequency of a stretched string related to : (i) its length? (ii) its tension? (2) (e) Define specific resistance and state its SI unit. (2) Answer 3. (a) A A D i e B i = e (b) V = 330 ms 1, C f = 20 Hz \ V=fl \ 330 = 20 l l= 330 20 lhighest = 16.5 m V = 330 Hz, f = 20,000 Hz \ V=fl \ 330 =l 20000 \ llowest = 0.0165 m = 1.65 10 2 m \ Range of wavelength from 20 Hz to 20000 Hz is 16.5 m to 1.65 10 2 m. (c) D = 300 km = 300000 m V = 3 108 ms 1 Ph- 91 \ S= 2017 2D T \ 3 108 = \ T= 2 300000 T 2 300000 3 108 = 2 10 3 s 1 (d) (i) Frequency of a stretched string is inversely proportional to its length. f l (ii) Frequency of a stretched string is directly proportional to its tension. f T (e) Specific resistance of a conductor is the resistance of unit length of the conductor and of unit area of cross section. Its SI unit is W m. Question 4. (a) An electric bulb of resistance 500 W draws a current of 0.4 A. Calculate the power of the bulb and the potential difference at its end. (b) State two causes of energy loss in a transformer. (c) State two characteristics of a good thermion emitter. (d) State two factors upon which the rate of emission of thermions depends. (e) When does the nucleus of an atom tend to be radioactive? Answer 4. (a) R = 500 W P= I2R I = 0.4 A = (0.4)2 500 = 80 \ P = 80 W \ P = VI \ 80 = V 0.4 \ V= 80 0.4 V = 200 V (b) (i) Formation of Eddy currents the changing magnetic field induces current in the soft-iron core. (ii) Resistance of primary or secondary coil. (iii) Hysteresis magnetisation of the core is reversed. (c) (i) Low work function. (ii) High melting point. Ph- 92 2017 (d) (i) Nature of the surface. (ii) Temperature of the surface. (e) (i) When the number of neutrons is greater than the number of protons in the nucleus. (ii) When the atomic number of an element is more than 82. SECTION II (40 Marks) (Attempt any four questions from this Section) Question 5. (a) A uniform half-metre rule balances horizontally on a knife edge at the 29 cm mark when a weight of 20 gf is suspended from one end. (i) Draw a diagram of the arrangement. (ii) What is the weight of the half-metre rule? (3) (b) (i) A boy uses a single fixed pulley to lift a load of 50 kgf to some height. Another boy uses a single movable pulley to lift the same load to the same height. Compare the efforts applied by them. Give a reason to support your answer. (ii) How does uniform circular motion differ from uniform linear motion? (iii) Name the process used for producing electricity using nuclear energy. (3) (c) A pulley system with VR = 4 is used to lift a load of 175 kgf through a vertical height of 15 m. The effort required is 50 kgf in the downward direction (g = 10 N kg 1). (i) Distance moved by the effort. (ii) Work done by the effort. (iii) MA of the pulley system. (iv) Efficiency of the pulley system. (4) Answer 5. (a) (i) 0 25 29 50 W gf (ii) By principle of moments Anticlockwise moment = clockwise moment \ f1d1 = f2d2 \ W 4 = 20 21 \ W 105 gf \ Weight of the rule = 105 gf (b) For a single fixed pulley, MA = 1 (i) \ Load = Effort \ Effort = 50 kgf For a single movable pulley, MA = 2 \ MA = Load Effort Ph- 93 \ 2017 50 =2 Effort \ Effort = 25 kgf \ Effort applied using a single fixed pulley 50 =2:1 = Effort applied using a single movable pulley 25 Effort applied by the boy using a single fixed pulley is twice the effort used by the boy using a single movable pulley. (ii) Uniform circular motion has variable velocity and hence variable acceleration. Uniform linear motion has constant velocity and no acceleration and \ is un accelerated motion. (iii) Nuclear fission. (c) (i) Velocity ratio = VR = \ 4= dE dL dE 15 \ dE = 60 m (ii) Work done by effort = Effort E Distance dE E = 50 kgf = 50 10 = 500 N \ Work done by effort = 500 N 60 m = 30000 J (iii) MA = L 175 = = 3.5 E 50 (iv) Efficiency = MA 3.5 100% = 100% = 87.5% VR 4 Question 6. (a) (i) How is the transference of heat energy by radiation prevented in a calorimeter? (ii) You have a choice of three metals, A, B and C, of specific heat capacities 900 Jkg 1 C 1, 380 Jkg 1 C 1 and 460 Jkg 1 C 1 respectively, to make a calorimeter. Which material will you select? Justify your answer? (3) (b) Calculate the mass of ice needed to cool 150 g of water contained in a calorimeter of mass 50 g at 30 C such that the final temperature is 5 C. (3) Specific heat capacity of calorimeter 0.4 J/g C Specific heat capacity of water 4.2 J/g C Latent heat capacity of ice 330 J/g (c) (i) Name the radiations which are absorbed by greenhouse gases in the earth's atmosphere. (ii) A radiation X is focused by a particular device on the bulb of a thermometer and mercury in the thermometer shows a rapid increase. Name the radiation X. (iii) Name two factors on which the heat energy liberated by a body depends. (4) Ph- 94 2017 Answer 6. (a) (i) The outer and inner surfaces of the calorimeter are polished to reduce loss of heat due to radiation. (ii) Metal B, since metal B has lowest specific heat capacity among the three. So the amount of heat energy taken by the calorimeter from its contents to acquire the temperature of its contents is negligible. (b) Heat gained by ice = mL + mc DT = m(330 + 4.2 5) = 351 mJ Heat given out by water and calorimeter = (150 4.2 + 50 .4) (32 5) = 17550 J Mass of ice = 17550 = 50 g 351 (c) (i) Infrared radiations of loy wavelength. (ii) Infrared radiations. (iii) Mass, specific heat capacity. Question 7. (a) A lens forms an upright and diminished image of an object when the object is placed at the focal point of the given lens. (i) Name the lens. (ii) Draw a ray diagram to show the image formation. (3) (b) A ray of light travels from water to air as shown in the diagram given below : Air 1= 48 Water (i) Copy the diagram and complete the path of the ray. Given that the critical angle for water is 48 . (ii) State the condition so that total internal reflection occurs in the above diagram. (3) (c) The diagram below shows a point source P inside a water container. Four rays A, B, C, D starting from the source P are shown up to the water surface. Air B A C 48 D Water P Ph- 95 2017 (i) Show in the diagram the path of these rays after striking the water surface. The critical angle for water-air surface is 48 . (ii) Name the phenomenon which the rays B and D exhibit. (4) Answer 7. (a) (i) Concave lens. (ii) B B O A F1 A F2 Image is between F and O. It is virtual, erect and diminished. (b) (i) Air Water 48 (ii) (1) The ray of light must travel from denser medium to rarer medium. (2) The angle of incidence should be greater than the critical angle. (c) (i) Air B A C 48 D i r Water P (ii) Ray B exhibits refraction of light. Ray D exhibits total internal reflection of light. Question 8. (a) Name the factor that determines : (3) (i) Loudness of the sound heard. (ii) Quality of the note. (iii) Pitch of the note. (b) (i) What are damped vibrations? (3) (ii) Give one example of damped vibrations. (iii) Name the phenomenon that causes a loud sound when the stem of a vibrating tuning fork is kept pressed on the surface of a table. Ph- 96 2017 (c) (i) A wire of length 80 cm has a frequency of 256 Hz. Calculate that length of a similar wire under similar tension, which will have a frequency of 1024 Hz. (4) (ii) A certain sound has a frequency of 256 hertz and a wavelength of 1.3 m. (1) Calculate the speed with which this sound travels. (2) What difference would be felt by a listener between the above sound and another sound travelling at the same speed, but of wavelength 2.6 m? Answer 8. (a) (i) Amplitude (ii) Waveform (iii) Frequency (b) (i) The periodic vibrations of a body of decreasing amplitude in presence of a resistive force are called damped vibrations. (ii) Oscillations of a simple pendulum in air. A tuning fork when struck on a rubber pad. (iii) Resonance (c) (i) Length of wire 1 Frequency f1 l2 = f 2 l1 \ L1 f1 = L2 f2 \ 80 cm 256 Hz = L2 1024 Hz \ L2 = 20 cm \ Length of the wire = 20 cm. (ii) (1) V = f l = 256 1.3 = 332.8 ms 1 (2) As V = f l \ 332.8 = f 2.6 \ f = 128 Hz. Since the frequency of this sound is half of the first one the listener would feel the sound to be less shrill or flat. Question 9. (a) (i) Name the colour code of the wire which has connected to the metallic body of an appliance. (ii) Draw the diagram of a dual control switch when the appliance is switched 'ON'. (3) (b) (i) Which particles are responsible for current in conductors? (ii) To which wire of a cable in a power circuit should the metal case of a geyser be connected? (iii) To which wire should the fuse be connected? (3) (c) (i) Explain the meaning of the statement 'current rating of a fuse is 5A'. (ii) In the transmission of power the voltage of power generated at the generating stations is stepped up from 11 kV to 132 kV before it is transmitted. Why? (4) Ph- 97 2017 Answer 9. (a) (i) Green or yellow. Load (ii) N a b c S1 S2 Supply a b c L (b) (i) Electrons (ii) Earth wire (iii) Live wire (c) (i) The live wire or the line wire has a current-carrying capacity of 5 A. Hence, a thin fuse wire of low current-carrying capacity of 5 A is used. It is used for light and fan circuits. (ii) The voltage is increased to decrease the current and prevent loss of energy due to heating in the line wires. Question 10. (a) Answer the following questions based on a hot cathode ray tube. (3) (i) Name the charged particles. (ii) State the approximate voltage used to heat the filament. (iii) What will happen to the beam when it passes through the electric field? (b) State three factors on which the rate of emission of electrons from a metal surface depends. (3) (c) (i) What are the free electrons? (ii) Why do they not leave the metal surface on their own? (iii) How can they be made to leave the metal surface? (State any two ways) (4) Answer 10. (a) (i) Cathode rays / high speed electrons (ii) 6 V (iii) The electron beam gets deflected towards the positive plate in a direction opposite to the direction of the electric field. (b) (i) The nature of the metal surface (ii) The temperature of the surface (iii) The surface area of the metal. (c) (i) Electrons in the outer orbits are weakly attracted by the nucleus. They are loosely bound and leave their individual atom and become free to move inside the solid. These electrons are called free electrons. (ii) The free electrons do not have sufficient kinetic energy to leave its surface. (iii) The free electrons can leave the metal surface by (1) Thermionic emission: when energy is supplied as heat. (2) Photo-electric emission: when energy is supplied as light. ICSE EXAMINATION QUESTION PAPER 2018 (SOLVED) SCIENCE Paper I (PHYSICS) (One hour and a half hours) Answers to this paper must be written on the paper provided separately. You will NOT be allowed to write during the first 15 minutes. This time is to be spent in reading the question paper. The time given at the head of this paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. SECTION I (40 Marks) (Attempt all questions from this Section) Question 1. (a) (i) State and define the SI unit of power. (ii) How is the unit horse power related to the SI unit of power? (2) (b) State the energy changes in the following cases while in use : (2) (i) An electric iron. (ii) A ceiling fan. (c) The diagram below shows a lever in use : (2) (i) To which class of levers does it belong? (ii) Without changing the dimensions of the lever, if the load is shifted towards the fulcrum what happens to the mechanical advantage of the lever? E F L (d) (i) Why is the ratio of the velocities of light of wavelengths 4000 A and 8000 A in vacuum 1 : 1? (ii) Which of the above wavelengths has a higher frequency? (2) (e) (i) Why is the motion of a body moving with a constant speed around a circular path said to be accelerated? (ii) Name the unit of physical quantity obtained by the formula 2K/V2 where K: kinetic energy, V: Linear velocity. (2) Answer 1. (a) (i) The SI unit of power is watt (W). The power of an agent is said to be one watt if it does one joule of work in one second. (ii) 1 hp = 746 W Ph- 98 2018 Ph- 99 (b) (i) (ii) (c) (i) (ii) (d) (i) 2018 Electrical into heat energy Electrical into mechanical energy. Second class lever. It increases. Because all wavelengths of light travel with the same velocity in vacuum. (ii) 4000 A higher frequency.. (e) (i) Because at every point of motion the direction of speed changes i.e., the body possesses velocity which changes with time. (ii) Kilogram (kg). Question 2. (a) The power of a lens is -5D. (2) (i) Find its focal length. (ii) Name the type of lens. (b) State the position of the object in front of a converging lens if : (2) (i) It produces a real and same size image of the object. (ii) It is used as a magnifying lens. (c) (i) State the relation between the critical angle and the absolute refractive index of a medium. (ii) Which colour of light has a higher critical angle? Red light or Green light. (2) (d) (i) Define scattering. (2) (ii) The smoke from a fire looks white. Which of the following statements is true? (1) Molecules of the smoke are bigger than the wavelength of light. (2) Molecules of the smoke are smaller than the wavelength of light. (e) The following diagram shows a 60 , 30 , 90 glass prism of critical angle 42 . Copy the diagram and complete the path of incident ray AB emerging out of the prism marking the angle of incidence on each surface. (2) X 60 B 30 Y Z A Answer 2. 1 1 = = 0.2 m = 20 cm P -5 (ii) Concave (b) (i) At 2F (ii) Between the optical center and principle focus. (a) (i) f = Ph- 100 2018 1 (c) (i) m = sin C (ii) Red (d) (i) Scattering is a general physical process where light is forced to deviate from a straight trajectory by one or more paths due to localized non-uniformities in the medium through which it passes. (ii) Molecules of the smoke are bigger than the wavelength of light. (e) The diagram is as shown X 60 45 45 B Y 30 Z A Question 3. (a) Displacement distance graph of two sound waves A and B, travelling in a medium, are as shown in the diagram below. (2) 20 10 (0, 0) A B Distance (cm) -10 -20 Study the two sound waves and compare their: (i) Amplitudes (ii) Wavelengths (b) You have three resistors of values 2 W, 3 W and 5 W. How will you join them so that the total resistance is more than 7 W? (2) (i) Draw a diagram for the arrangement. (ii) Calculate the equivalent resistance. (c) (i) What do you understand by the term nuclear fusion? (2) (ii) Nuclear power plants use nuclear fission reaction to produce electricity. What is the advantage of producing electricity by fusion reaction? Ph- 101 2018 (d) (i) What do you understand by free vibrations of a body? (2) (ii) Why does the amplitude of a vibrating body continuously decrease during damped vibrations? (e) (i) How is the emf across primary and secondary coils of a transformer related with the number of turns of coil in them? (2) (ii) On which type of current do transformers work? (2) Answer 3. (a) (i) AA / AB = 20 / 10 = 2 / 1 = 2 : 1 Amplitudes of A and B are in the ratio 2 : 1 (ii) lB > lA Wavelength of A and B are in the ratio 1 : 2 (b) (i) All of these can be connected in series as shown 2W 3W 5W (ii) R = 2 + 3 + 5 = 10 W (c) (i) It is a process in which two or more smaller nuclei combine to form a bigger nucleus. (ii) The product formed is not radioactive hence less harmful to humans / energy produced per nucleon is more them fission. (d) (i) If a body vibrates with its own frequency it is called a free vibration. (ii) Energy is used up in overcoming friction. (e) (i) e.m.f. and the number of turns of the coil are directly proportional = VP NP = VS NS (ii) Alternating current. (A.C.) Question 4. (a) (i) How can a temperature in degree Celsius be converted into SI unit of temperature? (2) (ii) A liquid X has the maximum specific heat capacity and is used as a coolant in Car radiators. Name the liquid X. (b) A solid metal weighing 150 g melts at its melting point of 800 C by providing heat at the rate of 100 W. The time taken for it to completely melt at the same temperature is 4 mm. What is the specific latent heat of fusion of the metal? (2) (c) Identify the following wires used in a household circuit : (2) (i) The wire is also called as the phase wire. (ii) The wire is connected to the top terminal of a three-pin socket. (d) (i) What are isobars? (ii) Give one example of isobars. (e) State any two advantages of electromagnets over permanent magnets. (2) Answer 4. (a) (i) 1 C = 273 K (ii) Water (b) Using Q = mL, 100 4 60 = 150 10 3 L or L = 100 4 60 = L = 1.6 105 J kg 1 150 10 -3 Ph- 102 2018 (c) (i) Live wire (ii) Earth wire (d) (i) Elements having same mass number but different atomic number. (ii) 14 14 23 23 6 C, 7 N and 12 Mg, 11 Na (e) (i) Strength can be increased or decreased during working. (ii) Polarities can be changed during working. SECTION II (40 Marks) (Attempt any four questions from this Section) Question 5. (a) (i) Derive a relationship between SI and C.G.S. unit of work. (3) (ii) A force acts on a body and displaces it by a distance S in a direction at an angle q with the direction of force. What should be the value of q to get the maximum positive work? (b) A half metre rod is pivoted at the centre with two weights of 20 gf and 12 gf suspended at a perpendicular distance of 6 cm and 10 cm from the pivot respectively as shown below: (3) 50 cm 20 gf 12 gf 6 cm 10 cm (i) Which of the two forces acting on the rigid rod causes clockwise moment? (ii) Is the rod in equilibrium? (iii) The direction of 20 kgf force is reversed. What is the magnitude of the resultant moment of the forces on the rod? (c) (i) Draw a diagram to show a block and tackle pulley system having a velocity ratio of 3 marking the direction of load (L), effort (E) and tension (T). (ii) The pulley system drawn lifts a load of 150 N when an effort of 60 N is applied. Find its mechanical advantage. (iii) Is the above pulley system an ideal machine or not? Answer 5. (a) (i) 1 J = 1 kg 1 m2 1 s 2 = 103 g 104 cm2 1 s 2 g cm2 s 2 = 107 erg (ii) W = FS cos q = FS (maximum) if cos q = 1 or q = 0 (b) (i) 12 kgf (ii) Yes (4) Ph- 103 2018 (iii) 120 + 120 = 240 dyne cm (c) (i) The diagram is as shown T E T T T L (ii) Actual MA number of pulleys in the system = 3. Observed MA = load 150 = = 2.5 effort 60 (iii) Since, observed MA is lesser than the theoretical MA therefore, the machine is not an ideal machine. Question 6. (a) A ray of light XY passes through a right angled isosceles prism as shown below. (3) A 45 Y X 45 C B (i) What is the angle through which the incident ray deviates and emerges out of the prism? (ii) Name the instrument where this action of prism is put into use. (iii) Which prism surface will behave as a mirror? (b) An object AB is placed between O and F1 on the principal axis of converging lens as shown in the diagram. (3) A 1F1 F1 B O LENS F2 2F2 Ph- 104 2018 Copy the diagram and by using three standard rays starting from point A, obtain an image of the object AB. (c) An object is placed at a distance of 12 cm from a convex lens of focal length 8 cm. Find : (4) (i) the position of the image (ii) nature of the image. Answer 6. (a) (i) 90 (ii) Refracting Periscope (iii) Surface AB (b) The figure is as shown. (c) Given u = 12 cm, f = +8 cm, v = ?, nature = ? Using the lens formula 1 1 1 we have = f v u 1 1 1 1 1 3- 2 1 = = = f + = + v u 8 - 12 24 24 Or v = 24 cm, (ii) Image will be real or inverted. Question 7. (a) Draw the diagram of a right angled isosceles prism which is used to make an inverted image erect. (3) (b) (3) Wooden Box Sonometer Paper rider 10 kg Tuning Fork A Tuning Fork B The diagram above shows a wire stretched over a sonometer. Stems of two vibrating tuning forks A and B are touched to the wooden box of the sonometer. It is observed that the paper rider (a small piece of paper folded at the centre) present on the wire flies off when the stem of vibrating tuning fork B is touched to the wooden box but the paper just vibrates when the stem of vibrating tuning fork A is touched to the wooden box. (i) Name the phenomenon when the paper rider just vibrates. (ii) Name the phenomenon when the paper rider flies off. (iii) Why does the paper rider fly off when the stem of tuning fork B is touched to the box? (c) A person is standing at the sea shore. An observer on the ship, which is anchored in between a Ph- 105 2018 vertical cliff and the person on the shore, fires a gun. The person on the shore hears two sounds, 2 seconds and 3 seconds after seeing the smoke of the fired gun. If the speed of sound in the air is 320 m s 1 then calculate : (i) the distance between the observer on the ship and the person on the shore. (ii) the distance between the cliff and the observer on the ship. (4) Cliff Man Observer Ship Sea shore Water Answer 7. (a) The diagram is as shown. A P 45 45 Object Q 90 Q C 45 45 Image P B (b) (i) Forced vibrations (ii) Resonance (iii) The wire of the sonometer begins to vibrate with its natural frequency. This is called resonance. At resonance the amplitude of vibration becomes very large. (c) Let distance between the observer on the ship and person on the shore be x. For the first sound which the person hears after 2 seconds, we have v= x x = vt = 320 2 = 640 m t Let distance between the ship and the cliff be x, then in the second case v= 2 x + 640 2x + 640 = vt = 320 3 = 960 t Or 2x = 960 640 = 320 m x= 320 = 160 m 2 Question 8. (a) (i) A fuse is rated 8 A. Can it be used with an electrical appliance rated 5 kW, 200 V? Give a Ph- 106 2018 reason. (3) (ii) Name two safety devices which are connected to the live wire of a household electric circuit. (b) (i) Find the equivalent resistance between A and B. 6W 4W B A 3W 12 W (ii) State whether the resistivity of a wire changes with the change in the thickness of the wire. (c) An electric iron is rated 220 V, 2 kW. (4) (i) If the iron is used for 2 h daily find the cost of running it for one week if it costs ` 4.25 per kWh. (ii) Why is the fuse absolutely necessary in a power circuit? Answer 8. (a) (i) The current which will pass through the electrical device will be I = P 5000 = = 25 A. V 200 The fuse cannot be used as it will blow off when the current exceeds 8 A. (ii) MCB Fuse, switch, ELCB. (b) (i) 6 W and 3 W are in parallel therefore, 6 3 18 =2W = 6+3 9 4 W and 12 W are in parallel therefore, 4 12 48 = =3W 4 + 12 16 The above two are now in series therefore, R = 2 + 3 = 5W (ii) Resistivity is independent of the dimensions of the wire. Therefore, no change. (c) (i) V = 220 V, P = 2 kW = 2000 W P (in watt) t (in hour) 2000 2 7 = = 28 kW h 1000 1000 Hence cost = 28 4.25 = ` 119 Energy consumed E = (ii) Power circuits draw large amount of current, Electric shock in this circuit is very fatal hence to avoid it fuse is necessary in the power circuit. Question 9. (a) (i) Heat supplied to a solid change it into liquid. What is this change in phase called? (3) (ii) During the phase change does the average kinetic energy of the molecules of the substance increase? (iii) What is the energy absorbed during the phase change called? (b) (i) State two differences between "Heat Capacity" and "Specific Heat Capacity". (3) Ph- 107 2018 (ii) Give a mathematical relation between Heat Capacity and Specific Heat Capacity. (c) The temperature of 170 g of water at 50 C is lowered to 5 C by adding certain amount of ice to it. Find the mass of ice added. Given: Specific heat capacity of water = 4200 J kg 1 C 1 and Specific latent heat of ice 336000 J kg 1. (4) Answer 9. (a) (i) Melting (ii) No (iii) Latent heat of fusion. (b) (i) The two differences are Specific heat capacity Heat capacity 1. Heat required to raise the temperature of a unit mass of a substance by 1 degree Celsius. 2. Does not depends upon the mass of the 1. Heat required to raise the temperature of a substance by 1 degree Celsius. 2. Depend upon of mass of the substance. substance. (ii) The relation is, heat capacity = Specific heat Mass of substance. (c) Given mass of ice = mg Mass of water = 170 g Initial temperature of water = 50 C Let the final temperature of the mixture = 5 C The latent heat required to change m g of ice at 0 C to m g of water at 0 C = m 336 = 336 m J Now, heat required to change m g of water at 0 C to 5 C = m 4.2 (5 0) J = 21 m J Now, heat lost by 170 g of water to reach 5 C from 50 C = 170 4.2 (50 5) = 32 130 J By principle of calorimetry Heat lost = Heat gained 336 m + 21 m = 32130 or 357 m = 32130 m = 90 g Question 10. (a) The diagram shows a coil wound around a U shape soft iron bar AB. A B + - Ph- 108 2018 (i) What is the polarity induced at the ends A and B when the switch is pressed? (ii) Suggest one way to strengthen the magnetic field in the electromagnet. (iii) What will be the polarities at A & B if the direction of current is reversed in the circuit? (3) (b) The ore of Uranium found in nature contains 92U238 and 92U235. Although both the isotopes are fissionable, it is found out experimentally that one of the two isotopes is more easily fissionable. (i) Name the isotope of Uranium which is easily fissionable. (ii) Give a reason for your answer. (iii) Write a nuclear reaction when Uranium 238 emits an alpha particle to form a Thorium (Th) nucleus. (3) (c) Radiations given out from a source when subjected to an electric field in a direction perpendicular to their path are shown below in the diagram. The arrows show the path of the radiation A, B and C. Answer the following questions in terms of A, B and C. (4) (i) Name the radiation B which is unaffected by the electrostatic field. (ii) Why does the radiation C deflect more than A? B A C + Radioactive Substance Lead Box (iii) Which among the three causes the least biological damage externally? (iv) Name the radiation which is used in carbon dating. Answer 10. (a) (i) A South and B South. (ii) Increasing the strength of current through the coil. (iii) The Polarities of the two ends become north. (b) (i) 92U235 (ii) It readily absorbs thermal neutrons and becomes unstable. (iii) The reaction is 238 90Th234 + 2He4 92U (c) (i) Gamma radiation (ii) Because C is lighter than A. (iii) Alpha (A) (iv) Carbon-14 ICSE EXAMINATION QUESTION PAPER 2019 (SOLVED) SCIENCE Paper I (PHYSICS) (One hour and a half hours) Answers to this paper must be written on the paper provided separately. You will NOT be allowed to write during the first 15 minutes. This time is to be spent in reading the question paper. The time given at the head of this paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. SECTION I (40 Marks) (Attempt all questions from this Section) Question 1. (a) The diagram below shows a claw hammer used to remove a nail; [2] Claw hammer Nail (i) To which class of lever does it belong? (ii) Given one more example of the same class of lever mentioned by you in (i) for which the mechanical advantage is greater than one. (b) Two bodies A and B have masses in the ratio 5:1 and their kinetic energies are in the ratio 125:9. Find the ratio of their velocities. [2] (c) (i) Name the physical quantity which is measured in calories. (ii) How is calories related to the S.I. unit of that quantity? (d) (i) Define couple. (ii) State the S.I. unit of moment of couple. (e) (i) Define critical angle. (ii) State one important factor which affects the critical angle of a given medium. Ph- 109 2019 Ph- 110 2019 Answer 1. (a) (i) It belongs to class I lever. (ii) The mechanical advantage is greater than one when effort arm of body is longer than the load arm. For example : crowbar, shears. (b) body A body B m1 = 5 x m2 = 1x K.E.1 = 125y K.E.2 = 9y 1 K.E. = mv 2 2 1 K.E 1 = m1 (v1 ) 2 2 K.E 1 1 m (v )2 1 = m1 (v1 ) 2 m2 (v2 )2 = 1 1 2 K.E 2 2 2 m2 (v2 ) 125 y (v1 ) 2 . m1 = 9y (v2 ) 2 . m2 (v1 )2 (v2 )2 (v1 ) 2 (v2 )2 = 125 m2 9 m1 = 125 1x 9 5x v1 25 = v2 9 v1 5 = v2 3 (c) (i) Heat energy is measured in calories (ii) SI unit is Joule. 1 calorie = 4.18 J (d) (i) Couple Two equal and opposite parallel forces, not acting along the same line, form a couple. (ii) Couple d O F F Ph- 111 2019 Moment of couple = F d = N m SI unit of moment of couple = Nm or Joule. (e) (i) Critical angle is angle of incidence in denser medium corresponding to which angle of refraction in rarer medium is 90 . (ii) Refractive index and wavelength. Question 2. (a) An electromagnetic radiation is used for photography in fog. [2] (i) Identify the radiation. (ii) Why is this radiation mentioned by you, ideal for this purpose? (b) (i) What is the relation between the refractive index of water with respect to air (amw) and the refractive index of air with respect to water (wma). (ii) If the refractive index of water with respect to air (amw) is 5 . 3 Calculate the refractive index of air with respect to water (wma). (c) The specific heat capacity of a substance A is 3,800 Jkg 1K 1 and that of a substance B is 400 Jkg 1K 1. Which of the two substances is a good conductor of heat? Give a reason for your answer. [2] (d) A man playing a flute is able to produce notes of different frequencies. If he closes the holders near his mouth, will the pitch of the note produced, increase or decrease? Given a reason. [2] (e) The diagram below shows a light source P embedded in a rectangular glass block ABCD of critical angle 42 . Complete the path of the ray PQ till it emerges out of the block. [Write necessary angles.] [2] B Q C 42 P A D Answer 2. (a) (i) Infrared radiations. (ii) Infrared radiations are used for this purpose or they are not scattered much and can penetrate appreciably through it. (b) (i) w ma a mw = 1 Ph- 112 2019 According to principle of reversibility a mw = (ii) a m w = w ma 1 w ma 5 3 =? According to principle of reversibility a mw w ma (c) = 1 w ma = 1 1 3 = = m 5 / 3 5 a w A B 1 1 Specific heat Capacity = 3,800 Jkg K C = 400 JKg 1 Substance B is good conductor of heat. Reason B has high conductivity because it has low specific heat capacity.. Low specific heat capacity = good conductor of heat. (d) Pitch decreases as length of air column increases in flute. Q (e) 42 42 48 48 90 48 42 P 90 Question 3. (a) (i) If the lens is placed in water instead of air, how does its focal length change? (ii) Which lens, thick or thin has greater focal length? (b) Two waves of the same pitch have amplitudes in the ratio 1: 3. What will be the ratio of their: [2] [2] Ph- 113 2019 (i) Intensities and (ii) Frequencies? (c) How does an increase in the temperature affect the specific resistance of a : (i) Metal and [2] (ii) Semiconductor? (d) (i) Define resonant vibrations. [2] (ii) Which characteristic of sound, makes it possible to recognize a person by his voice without seeing him? (e) It is possible for a hydrogen (H) nucleus to emit an alpha particle? [2] Answer 3. (a) (i) Local length will. (ii) Thin lens has greater focal length. (b) (i) Amplitude = 1 : 3 2 1 1 Intensities = = 3 9 (ii) Frequency does not depends upon amplitude. \ its ratio is 1 : 1. (c) (i) Metal increase (ii) Semiconductor decrease (d) (i) Resonant vibrations occurs due to phenomenon of Resonance. It occurs due to resonance. It is special case of forced vibrations when frequency of externally applied force on body is equal to its natural frequency, body readily begins to vibrate with increased amplitude. Vibrations of large amplitude are called resonant vibrations. (ii) pitch. (e) No it is not possible. It has not enough electrons and protons for emitting alpha particle. Question 4. (a) Calculate the effective resistance across AB : [2] 4W 5W 8W B A 3W (b) (i) State whether the specific heat capacity of a substance remains the same when its state changes from solid to liquid. Ph- 114 2019 (ii) Given one example to support your answer. [2] (c) A magnet kept at the centre of two coils A and B is moved to and fro as shown in the diagram. The two galvanometers show deflection. [2] Soft iron N Soft iron S X Y Cell A Cell B (d) State with a reason whether: x > y or x < y [x and y are magnitudes of deflection.] [2] (i) Why a nuclear fusion reaction is called a thermos nuclear reaction? (ii) Complete the reaction: 3He 2 + 2H1 4He2 +................+ Energy (e) State two ways to increase the speed of rotation of a D.C. motor. [2] Answer 4. (a) R 1 = 9W R 2 = 3W R 3 = 8W 4W 5W 1 1 1 = + R p R1 R 2 8W 3W A B 1 1 1 = + Rp 9 3 1 1+ 3 4 = = Rp 9 9 Rp = 9W 8W 9 4 A RS = R3 + Rp RS = 9 +8 4 RS = 9 + 32 41 = = 10 2W 4 4 (b) (i) No, specific heat capacity changes from solid to liquid. 3W B Ph- 115 2019 (ii) For e.g. ice and water have different specific heat capacity. (c) y > x because (y) coil B have more number of turns. (d) (i) Nuclear fusion is called Thermo nuclear reaction as it not occurs in ordinary temperature. It need about 107 Kelvin temperature. (ii) 23 He + 21 H 42 He + Energy + 11H SECTION II (40 Marks) Attempt any four questions from this Section Question 5. (a) A body of mass 10 Kg is kept at a height of 5 m. It is allowed to fall and reach the ground.[3] (i) What is the total mechanical energy possessed by the body at the height of 2m assuming it is a frictionless medium? (ii) What is the kinetic energy possessed by the body just before hitting the ground? Take g = 10m/s2. (b) A uniform meter scale is in equilibrium as shown in the diagram: [3] 30 cm 5 cm F 0 cm 100 cm 40 gf (i) Calculate the weight of the meter scale. (ii) Which of the following options is correct to keep the ruler in equilibrium when 40 gf wt is shifted to 0 cm mark? F is shifted towards 0 cm. or F is shifted towards 100 cm. (c) The diagram below shown a pulley arrangement : [4] (i) Copy the diagram and mark the direction of tension on each stand of the string. B E (ii) What is the velocity ratio of the arrangement? (iii) If the tension acting on the string is T, then what is the relationship between T and effort E? (iv) If the free end of the string moves through a distance x, find the distance by which the load is raised. A Load Ph- 116 2019 Answer 5. (a) K.E. = Kinetic enegy m = 10 kg g = 10 T.E. = K.E. + (U) Potential energy h = 5m (i) V = mgh = 10 10 5 = 500 J K.E. = 0 T.E. = U = 500 J \ When body is just to hit ground (ii) K.E. = U U = mgh then U = O U = 5 10 10 = 500 J T.E. = K.E. + U T.E. = K.E. + O T.E. = K.E. K.E. = 500 J (b) (i) According to principle of moment W1 l1 = W2 l2 40 (30 5) = W2 (50 30) 40 25 = W2 20 W2 = 50 g (ii) J is shifted towards 0 cm. (c) (i) B T T T E A Load dl (ii) Velocity ratio = 2 V.R. = d (iii) T = E dl = 2 x (iv) d = x d = x Ph- 117 2019 dL = ? \ V.R. = 2x =2 x V.R. = 2 d V.R. = d L 2= x x dL = dL 2 Question 6. (a) How does the angle of deviation formed by a prism change with the increase in the angle of incidence? [3] Draw a graph showing the variation in the angle of deviation with the angle of incidence at a prism surface. (b) A virtual, diminished image is formed when an object is placed between the optical centre and the principal focus of a lens. [3] (i) Name the type of lens which forms the above image, (ii) Draw a ray diagram to show the formation of the image with the above stated characteristics. (c) An object is placed at a distance of 24 cm from a convex lens of focal length 8 cm. [4] (i) What is the nature of the image so formed? (ii) Calculate the distance of the image from the lens, (iii) Calculate the magnification of the image. Answer 6. (a) First with increase in angle of incidence angle deviation first decrease to deviation minimum and then it increase. devation 8 min incidence Ph- 118 2019 (b) (i) concave lens (ii) Image is diminished and virtual. B 2F1 F1 A1 F2 2F2 (c) (i) Real image ` (ii) m = -24 cm, f = 8 cm, v = ? 1 1 1 = f v m 1 1 1 = + v f m 1 1 1 = v 8 24 1 3 -1 2 = = = 12cm v 24 24 (iii) m = \ V = 12 cm v 12 -1 = = m -24 2 Question 7. (a) It is observed that during march-past we hear a base drum distinctly from a distance compared to the side drums. [3] (i) Name the characteristic of sound associated with the above observation, (ii) Given a reason for the above observation. (b) A pendulum has a frequency of 4 vibrations per second. An observer starts the pendulum and fires a gun simultaneously. He hears the echo from the cliff after 6 vibrations of the pendulum. If the velocity of sound in air is 340 m/s, find the distance between the cliff and observer. [3] (c) Two pendulums C and D are suspended from a wire as shown in the figure given below. Pendulum C is made to oscillate by displacing it from its mean position. It is seen that D also starts oscillating. [4] Ph- 119 2019 wire C D (i) Name the type of oscillation, C will execute. (ii) Name the type of oscillation, D will execute. (iii) If the length of D is made equal to C then what difference will you notice in the oscillations of D? (iv) What is the name of the phenomenon when the length of D is made equal to C? Answer 7. (a) (i) Loudness is characteristic of sound associated with above observation. (ii) Surface area of bass drum is more therefore amplitude is more and it produces more loudness. ` (b) 4 vibration = 1 second (frequency of pendulum) 1 vibration = 1 second 4 6 vibration = 1 6 second 4 t= 6 second 4 Speed = 340 m/s = V For echo, d = Vt 340 6 = 255 m = 2 4 2 (c) (i) Forced oscillation as Pendulum C is made to oscillate by displacing it from mean position and it is not in vaccum. (ii) Resonant oscillation. (iii) If length of D is made equal to C then vibration of both will be same. (iv) Resonance. Ph- 120 2019 Question 8. (a) (i) Write one advantage of connecting electrical appliance in parallel combination. (ii) What characteristic should a fuse wire have? (iii) Which wire in a power circuit is connected to the metallic body of the appliance? (b) The diagram below shows a dual control switch circuit connected to a bulb. Bulb [3] [3] B A (i) Copy the diagram and complete it so that bulb is switch ON. (ii) Out of A & B which one is the live wire and which one is the neutral wire? (c) The diagram below shows a circuit with the key k open. Calculate : K 2W 3W 5W 3.3V, 0,5W (i) the resistance of the circuit when the key k is open. (ii) the current drawn from the cell when the key k is open. (iii) the resistance of the circuit when the key k is closed. (iv) the current drawn from the cell when the key k is closed. Answer 8. (a) (i) If both are in parallel combination then if one is damaged then other will not be damaged or effected. (ii) A fuse wire should have high resistivity and low melting point. (iii) Earth wire. (b) Bulb B A Ph- 121 2019 Bulb (i) B A (ii) A is line wire and B is neutral wire. (c) V = 3.3 V r = 0.5 W (i) R = (5 + 0.5) W = 5.5 W (ii) I = V 3/ 3 3 = = 0.6 W = R 5/5 5 (iii) R1 = 5W, R2 = R3 + R4, R2 = 5 W 1 1 1 = + Rp 5 5 Rp = 5 = 2 5W 2 R = (Rp + r) = (2.5 + 0.5) = 3 W (iv) I = V 3.3 = = 1.1A R 3 Question 9. (a) (i) Define Calorimetry. [3] (ii) Name the material used for making a Calorimeter. (iii) Why is a Calorimeter made up of thin sheets of the above material answered in (ii)? (b) The melting point of naphthalene is 80 C and the room temperature is 30 C. A sample of liquid naphthalene at 100 C is cooled down to the room temperature. Draw a temperature time graph to represent this cooling. In the graph, mark the region which corresponds to the freezing process. [3] (c) 104 g of water at 30 C is taken in a calorimeter made of copper of mass 42g. When a certain mass of ice at 0 C is added to it, the final temperature of the mixture after the ice has melted, was found to be 10 C. Find the mass of ice added. [Specific heat capacity of water = 4.2 Jg 1 C 1; Specific latent heat of fusion of ice = 336 Jg 1; Specific heat capacity of copper = 0.4 Jg 1 C1] [4] Ph- 122 2019 Answer 9. Temperature (a) (i) The measurement of heat energy that means heat lost or gained is called calorimetry. (ii) Copper. (iii) Copper has low specific heat capacity if we use thin sheetd, the thermal capacity further decreases therefore we made it thin sheets of copper. (b) 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 Freezing Time (S) (c) Hot bodies Cold body H2O 104 gm at 30 C Calorimeter = 42 gm at 30 C Ice x gm at 0 C (Copper) According to principle of calorimetery Heat lost = Heat gained Final temperature = 10 C Q = mcDt (104 (30 - 10) 4.2) + (42 (30 - 10) 0.4) = ( x 336) + ( x + 4.2 10 - 0) 8736 + 336 = 378x 9072 = 378x x= 9072 = 24gm 378 Question 10. (a) Draw a neat labeled diagram of an A.C. generator. [3] (b) (i) Define nuclear fission. [3] (ii) Rewrite and complete the following nuclear reaction by filling in the atomic number of Ba and mass number of Kr : 235 1 92 U + 0 n 144 ..... Ba + .... 36 Kr + 3 01n + Energy Ph- 123 2019 (c) The diagram below shows a magnetic needle kept just below the conductor AB which is kept in North South direction. [4] B A W S N E + K (i) In which direction will the needle deflect when the key is closed? (ii) Why is the deflection produced? (iii) What will be the change in the deflection if the magnetic needle is taken just above the conductor AB? (iv) Name one device which work on this principle. Answer 10. Axle (a) B C Armature core Soft iron core A Brush B S 1 1 D Slip rings S2 B 2 Slipring Brush Load (b) (i) Nuclear fission is process in which heavy nucleas is splitted into two or more light nuclei by bombarding in slow neutrons. It produces very much energy. 1 144 89 1 (ii) 235 92 u + 0 n 56 Ba + 36 Kr + 3n0 + Energy (c) (i) West (ii) because a current carrying conductor produces a magnetic field so deflection is produced. (iii) East (iv) Electromagnet or electric bell. ICSE QUESTION PAPER-2010 (SOLVED) PAPER 2 (CHEMISTRY) (One hour and a half) Answer to this paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the Question Paper. The time given at the head of this paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. SECTION - I (40 MARKS) (Attempt all questions) Question 1. (a) From the list given below, select the word(s) required to correctly complete the blanks (i) to (v) in the following passage : Note : Words chosen from the list are to be used only once. Write only the answers. Do not copy the passage. (reddish brown, ammonium, nitrogen dioxide, hydroxyl, dirty green, ammonia, acidic, alkaline) Nitrogen and hydrogen combine in the presence of a catalyst to give (i) ................. gas. When the above mentioned gas is passed through water it forms a solution which will be (ii) ................. in nature and the solution contains (iii) ................. ions and (iv) ................. ions. The above solution when added to iron (II) sulphate solution, given a (v) ................. coloured precipitate of iron (II) hydroxide. (5) Ans. (i) Ammonia (ii) Alkaline (iii) Ammonium (iv) Hydroxyl (v) Dirty green (b) Select from the list given (A to E) one substance in each case which matches the description given in parts (i) to (v). (Note : Each substance is used only once in the answer.) (A) Nitroso Iron (II) sulphate (B) Iron (III) chloride (C) Chromium sulphate (D) Lead (II) chloride (E) Sodium chloride. (i) A compound which is deliquescent. (ii) A compound which is insoluble in cold water, but soluble in hot water. (iii) The compound responsible for the brown ring during the brown ring test of nitrate ion. Ch- 124 2010 Ch- 125 2010 (iv) A compound whose aqueous solution is neutral in nature. (v) The compound which is responsible for the green coloration when sulphur dioxide is passed through acidified potassium dichromate solution. (5) Ans. (i) Iron (II) chloride (iii) Nitroso Iron (II) sulphate (ii) Lead (II) chloride (iv) Sodium chloride (v) Chromium sulphate (c) For part (c) (i) (c) (x), select the correct answer from the choice A, B, C and D which are given. Write only the letter corresponding to the correct answer. (i) (10) A particular solution contains molecules and ions of the solute so it is a : (a) weak acid (b) strong acid (c) strong base (d) salt solution Ans. (a) weak acid (ii) A compound which liberates reddish brown gas around the anode during electrolysis in its molten state is : (a) Sodium chloride (b) Copper (II) oxide (c) Copper (II) sulphate (d) Lead (II) bromide Ans. (d) Lead (II) bromide (iii) An organic compound undergoes addition reactions and gives a red colour precipitate with ammoniacal cuprous chloride. Therefore, the organic compound could be : (a) Ethane (b) Ethene (c) Ethyne (d) Ethanol (b) Sulphuric acid (d) Hydrochloric acid Ans. (c) Ethyne (iv) An organic weak acid is : (a) Formic acid (c) Nitric acid Ans. (a) Formic acid (v) During ionization metals lose electrons, this change can be called : (a) Oxidation (c) Redox (b) (d) Reduction Displacement Ans. (a) Oxidation (vi) Which one of the following in not true of metals : (a) Metals are good conductors of electricity (b) Metals are malleable and ductile (c) Metals form non-polar covalent compounds (d) Metal will have 1 or 2 or 3 electrons in their valence shell. Ch- 126 2010 Ans. (c) Metals form non-polar covalent compounds (vii) An example of a complex salt is : (a) Zinc sulphate (b) Sodium hydrogensulphate (c) Iron (II) ammonium sulphate (d) Tetrammine copper (II) sulphate Ans. (d) Tetrammine copper (II) sulphate (viii) Aqua regia is a mixture of : (a) Dilute hydrochloric acid and concentrated nitric acid (b) Concentrated hydrochloric acid and dilute nitric acid (c) Concentrated hydrochloric acid (1 part) and concentrated nitric acid (3 parts) (d) Concentrated hydrochloric acid (3 parts) and concentrated nitric acid (1 part) Ans. (d) Concentrated hydrochloric acid (3 parts) and concentrated nitric acid (1 part) (ix) The organic compound mixed with ethanol to make it spurious is : (a) Methanol (b) Methanoic acid (c) Methanal (d) Ethanoic acid Ans. (a) Methanol (x) The number of electrons present in the valence shell of a halogen is : (a) 1 (b) 3 (c) 5 (d) 7 Ans. (d) 7 (d) State your observation for the following cases : (i) Moist blue litmus is introduced into a gas jar of sulphur dioxide. (ii) Dry red rose petals are placed in the jar of sulphur dioxide. (iii) Paper soaked in potassium permanganate solution is introduced into a gas jar of sulphur dioxide. (iv) Ammonia gas is burnt in an atmosphere of oxygen in the absence of a catalyst. (v) Glass rod dipped in ammonium hydroxide is brought near the mouth of the concentrated hydrochloric acid bottle. (5) Ans. (i) Moist blue litmus turns red and finally colourless as SO 2 act as an acidic gas and then a bleaching agent. (ii) The colour of red rose petals gets bleached because SO 2 is a strong bleaching agent. (iii) The pink colour of potassium permanganate paper turns colourless because of bleaching property of sulphur dioxide. (iv) Greenish yellow flame is observed. (v) Dense white fumes of ammonium chloride are observed. (e) Match the column A with column B. Ch- 127 2010 Column A (i) Sodium chloride (ii) Ammonium ion Column B Increases Covalent bond (iii) Electronegativity across the period (iv) Non metallic character down the group (v) Carbon tetrachloride Answer as follows : Ionic bond Covalent and coordinate bond Decreases (i) correct item from B matching sodium chloride. (ii) correct item from B matching ammonium ion, and so on. Ans. Column A Column B (i) Sodium chloride Ionic bond (ii) (iii) (iv) (v) Ammonium ion Electronegativity across the period Non metallic character down the group Carbon tetrachloride (5) Covalent and coordinate bond Increases Decreases Covalent bond (f) Write the equation for each of the following reactions : (i) Sulphur is heated with concentrated sulphuric acid (ii) Zinc oxide is treated with sodium hydroxide solution. (iii) Ammonium chloride is heated with sodium hydroxide. (iv) Concentrated sulphuric acid is poured over sugar. (v) Magnesium sulphate solution is mixed with barium chloride solution. Ans. (i) (5) S + 2H2 SO4 3SO 2 + 2H2 O (ii) ZnO + 2NaOH Na 2 ZnO2 + H2 O (iii) NH4 Cl + NaOH NaCl + NH 3 + H2 O (iv) C12 H22 O11 + H2 SO4 12C + 11H2 O (v) MgSO4 + BaCl2 BaSO4 + MgCl 2 (g) (i) LPG stands for liquefied petroleum gas. Varieties of LPG are marketed including a mixture of propane (60%) and butane (40%). If 10 litre of this mixture is burnt, find the total volume of carbon dioxide gas added to the atmosphere. Combustion reaction can be represented as : C3 H8(g) + 502(g) 3CO2(g) + 4H2 O(g) 2C4 H10(g) + 13O2(g) 8CO2(g) + 10H2 O(g) (ii) Calculate the percentage of nitrogen and oxygen in ammonium nitrate. (Relative molecular mass of ammonium nitrate is 80, H = 1, N = 14, O = 16). (5) Ans. % of propane = 60% % of butane = 40% Ch- 128 2010 Total volume of the mixture = 10 litre _ Propane = _ Butane = (i) 60 10 = 6 litres 100 40 10 = 4 litres 100 Combustion of propane : C3 H8(g) + 5O2(g) 3CO 2(g) + 4H2 O(g) 1 vol 3 vol 6 litres ? 1 vol of propane releases 3 vol of CO 2 6 litres of propane releases 3 6 litres 1 (ii) Combustion of butane : 2C4 H10(g) + 13O 2(g) 8CO 2(g) + 10H 2 O(g) 2 vol 8 vol 1 vol 4 vol 4 litres ? 2 vol of butane releases 8 vol of CO2 4 litres of butane releases 8 4 = 16 l 2 Total CO2 released O 2 = 18 l + 16 l = 34 litres of CO2 gas is added to atmosphere (iii) NH4 NO3 [14 + (4 1) + 14 + (16 3)] [14 + 4 + 14 + 48] = 80 28 100 = 35% 80 % of nitrogen = % of oxygen = 48 100 = 60% 80 % of hydrogen = 4 100 = 5% 80 35% of nitrogen, 60% of oxygen and 5% of hydrogen Ch- 129 2010 SECTION - II (40 MARKS) (Attempt any four questions) Question 2. (a) Give the equation for the following conversions A to E. A ZnSO4 B ZnCO3 Zn(NO3)2 E C D ZnO (5) Zn(OH)2 Ans. A : ZNSO4 + Na 2 CO3 ZnCO3 + Na 2 SO4 zinc sodium zinc zinc sulphate carbonate carbonate sulphate B : ZnCO3 + 2HNO 3 Zn(NO3 ) 2 + H 2 O + CO2 zinc nitric carbonate acid zinc nitrate water zinc dioxide C : Zn(NO 3 ) 2 + 2NaOH Zn(OH) 2 + 2NaNO 3 zinc sodium zinc sodium nitrate hydroxide hydroxide nitrate D ZnO + H 2 O D : Zn(OH)2 zinc zinc hydroxide oxide water E : ZnO + H2 SO4 ZnSO4 + H2 O zinc sulphuric zinc oxide acid sulphate (b) The (i) (ii) (iii) (iv) (v) water questions below are related to the manufacture of ammonia. Name the process. In what ratio must the reactants be taken ? Name the catalyst used. Give the equation for the manufacture of ammonia. Ammonia can act as a reducing agent - write a relevant equation for such a reaction. (5) Ans. (i) Habers process (ii) N2 and H 2 in the ratio (1 : 3) (iii) Finely divided iron Ch- 130 2010 450 - 500 C (iv) N2 + 3H2 200 - 900 atm Fe + Mo 2NH3 + 22.4 K Cal (v) 2NH3 + 3Cl 2 N2 + 6HCl Question 3. (a) Draw the structural formula for each of the following : (i) Ans. (i) Ethanoic acid H H O C C (ii) OH But-2-yne (2) (Ethanoic acid) H H (ii) H C H (b) Mr. this (i) (iii) H C C C H (But-2-yne) H Ramu wants to electroplate his key chain with nickel to prevent rusting. For electroplating : Name the electrolyte (ii) Name the cathode Name the anode (iv) Give the reaction at the cathode (v) Give the reaction at the anode. Ans. (i) Nickel sulphate (iii) Nickel electrode (v) At Anode : Ni (s) 2e (5) (ii) Key chain (iv) At Cathode : Ni2+ + 2e Ni(s) Ni2+ (c) Three different electrolytic cells A, B and C are connected in separate circuits. Electrolytic cell A contains sodium chloride solution. When the circuit is completed a bulb in the circuit glows brightly. Electrolytic cell B contains acetic acid solution and in this case the bulb in the circuit glows dimly. The electrolytic cell C contains sugar solution and the bulb does not glow. Give a reason for each of these observation. (3) Ans. Cell A : Strong electrolyte (NaCl) Cell B : Weak electrolyte (Acetic acid) Cell C : Non electrolyte (Sugar solution) Question 4. Bulb glows brightly.. Bulb glows dimly.. Bulb doesn t glow.. (a) 4.5 moles of calcium carbonate are reacted with dilute hydrochloric acid. (i) Write the equation for the reaction. (ii) What is the mass of 4.5 moles of calcium carbonate ? (Relative molecular mass of calcium carbonate is 100). Ch- 131 2010 (iii) What is the volume of carbon dioxide liberated at stp ? (iv) What mass of calcium chloride is formed ? (Relative molecular mass of calcium chloride is 111). (v) How many moles of HCl are used in this reaction ? (5) CaCO 3 + 2HCl CaCl2 + H2 O + CO 2 100 111 (ii) 1 mole of calcium carbonate weighs 100 g 4.5 moles of calcium carbonate weighs 100 4.5 = 450g (iii) 1 mole of calcium carbonate liberates CO 2 = 22.4l 4.5 moles of calcium carbonates liberates CO 2 = 22.4 4.5 = 100.8 litres Ans. (i) (iv) CaCO3 + 2HCl CaCl2 + H2 O + CO 2 100g 111g From 100g CaCO 3 ; CaCl2 formed is 111g From 1g of CaCO 3 ; CaCl2 formed is 111 g 100 From 450g of CaCO 3 ; CaCl2 formed is 111 450 = 499.5g of CaCl2 100 (v) 2 moles of HCl are used in this reaction. (b) The diagram shows an apparatus for the laboratory preparation of hydrogen chloride. (i) Identify A and B (ii) Write the equation for the reaction. (iii) How would you check whether or not the gas jar is filled with hydrogen chloride? (iv) What does the method of collection tell you about the density of hydrogen chloride ? (5) Ch- 132 Ans. (i) 2010 A Sulphuric acid B Sodium chloride (ii) NaCl + H 2 SO4 Below 200 C NaHSO 4 + HCl Sodium Hydrogen bisulphate Chloride gas (iii) In order to know that the jar is filled with the gas, bring a glass rod dipped in ammonium hydroxide solution near its mouth. If dense white fumes of ammonium chloride are produced, it indicates that the gas jar is full of HCl gas. HCl + NH 3 NH4 Cl(s) (iv) The method used to collect HCl is Upward displacement of air . This clearly indicates that HCl gas is heavier than air. Question 5. (a) Name the main constituent metal in the following alloys : (i) Duralumin (ii) Brass (iii) Stainless steel (3) Ans. (i) Aluminium (ii) Zinc (iii) Iron (b) An element has an atomic number 16. State (i) the period to which it belongs. (ii) the number of valence electrons. (iii) whether it is a metal or non-metal (3) Ans. Atomic no. (16) 2 , 8 , 6 K L M (c) Ans. (d) Ans. (i) 3 period (Because it has three shells) (ii) 6 valence electrons (Valence electrons are present in outermost orbit) (iii) Non metal (elements having 5, 6, or 7 valence electrons are non metals) Solution A is a sodium hydroxide solution. Solution B is a weak acid. Solution C is dilute sulphuric acid. Which solution will (i) liberate sulphur dioxide from sodium sulphite. (ii) give a white precipitate with zinc sulphate solution. (iii) contain solute molecules and ions ? (3) (i) Solution C (ii) Solution A (iii) Solution B By the addition of only one solution how would you distinguish between dilute hydrochloric acid and dilute nitric acid ? (1) HCl (dilute) HNO3 (dilute) [To differentiate between HCl and HNO3 we can use AgNO 3 solution] Ch- 133 2010 HCl + AgNO3 AgCl + HNO 3 white ppt HNO3 + AgNO 3 No reaction By adding AgNO 3 , HCl gives white ppt whereas no such reaction takes place with HNO 3 . Question 6. (a) Give the equation for the preparation of each of the following salts from the starting material given. (i) Copper sulphate from copper (II) oxide. (ii) Iron (III) chloride from iron. (iii) Potassium sulphate from potassium hydroxide solution. (iv) Lead chloride from lead carbonate (two equations). Ans. (i) CuO + H2 SO2 CuSO4 + H2 O Copper (II) oxide Copper sulphate (ii) 2Fe + 3Cl2 2FeCl3 Iron Chlorine . Ferric chloride (iii) 2KOH + H 2 SO4 Temp. above 200 C Potassium hydroxide (iv) PbCO3 Lead carbonate + K2 SO4 + 2H 2 O Potassium sulphate 2HNO3 Pb(NO3 ) 2 Lead nitrate (Insoluble salt) + H2 O + CO2 (Soluble salt) Pb(NO3 ) 2 + 2HCl Lead nitrate PbCl2 + 2HNO 3 Lead chloride (b) Compound A is bubbled through bromine dissolved in carbon tetrachloride and the product is CH2 Br CH2 Br. A (i) B r2/CCl4 CH2 Br CH2 Br Draw the structural formula of A. (ii) What type of reaction has A undergone ? (iii) What is your observation ? (iv) Name (not formula) the compound formed when steam reacts with A in the presence of phosphoric acid. (v) What is the procedure for converting the product of (b) (iv) back to A ? (5) Ans. A (i) B r2/CCl4 H CH2 Br CH2 Br H H C C H (Ethene) (ii) Addition reaction Ch- 134 2010 (iii) Reddish brown colour of bromine gets discharged (iv) CH2 = CH2 + H2 O Phosphoric acid CH3 CH 2 OH Ethene (Ethanol) (v) By dehydration (with any dehydrating agent) C2 H5 OH Al2O 3 300 C Ethanol C2 H 4 + H 2O Ethene Question 7. (a) The diagram shows a simple arrangement of the fountain experiment : (i) Name the two gases you have studied which can be used in this experiment. (ii) What is the common property demonstrated by this experiment ? (3) Ans. (i) Hydrogen chloride gas (HCl) Ammonia (NH 3 ) (ii) Solubility of gases (b) Define the following terms : (i) Ionization potential Ans. (i) (ii) Electron affinity. (2) Ionisation Energy : It is the minimum amount of energy required to remove the most loosely bond electron from an isolated, neutral gaseous atom : M(g) + I.E. M+ (g) + e Ionization energy (ii) Electron affinity : It is the amount of energy released when an isolated neutral gaseous atom of an element takes up an extra electron to form uninegative gaseous ions. Ch- 135 2010 X(g) + e X (g) + E.A. Electron affinity (c) The action of heat on the blue crystalline solid L gives a reddish brown gas M, a gas which re-lights a glowing splint and leaves a black residue. When gas N, which has a rotten egg smell, is passed through a solution of L a black precipitate is formed. (i) Identify L, M and N (Name of formula) (ii) Write the equation for the action of heat on L (iii) Write the equation for the reaction between the solution of L and the gas N. D Ans. Cu(NO3 ) 2 CuO + NO2 + Electron affinity Black residue Brown coloured gas O2 Gas which rekindles a glowing splinter L M N = Rotten egg smell H2S Cu(NO3 ) 2 + H 2 S CuS + 2HNO 3 Black Precipitate (i) L = Copper nitrate [Cu(NO 3 ) 2 ] M = Oxygen (O2 ) N = Hydrogen sulphide (H 2 S) D CuO + NO2 + O2 (ii) Cu(NO3 ) 2 (iii) Cu(NO3 ) 2 + H 2 S CuS + 2HNO3 ICSE QUESTION PAPER-2011 (SOLVED) PAPER 2 (CHEMISTRY) (One hour and a half) Answer to this paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the Question Paper. The time given at the head of this paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. SECTION - I (40 MARKS) (Attempt all questions) Question 1. (a) Chosse from the following list of the substances, as to what matches the description from (i) to (v) given below : [Acetylence gas, aqua fortis, coke, brass, barium chloride, bronze, platinum]. (i) An aqueous salt solution used for testing sulphate radical. (ii) A catalyst used in the manufacture of nitric acid by Ostwald s process. (iii) A black powdery substance used for the reduction of zinc oxide during its extraction. (iv) A gaseous hydrocarbon commonly used for welding purposes. (v) The substance is an alloy of zinc, copper and tin. [5] (b) What would you observe in each of the following cases? (i) Ammonium hydroxide is first added in a small quantity and then in excess to a solution of copper sulphate. (ii) Sugar crystals are added to a hard glass test tube containing concentrated sulphuric acid. (iii) Copper is heated with concentrated nitric acid in a hard glass test tube. (iv) Water is added to the product formed, when aluminium is burnt in a jar of nitrogen gas. (v) When carbon monoxide is passed over heated copper oxide. [5] (c) Give reasons as to why : (i) the electrolysis of acidulated water is considered to be an example of catalysis. (ii) almost 90% of all known compounds are organic in nature. (iii) it is dangerous to burn methane in an insufficient supply of air. (iv) hydrogen chloride can be termed as a polar covalent compound. Ch- 136 2011 Ch- 137 (v) 2011 the oxidising power of elements increases on moving from left to right along a period in the periodic table. [5] (d) Fill in the blanks from the choices given below : (i) In covalent compounds, the bond is formed due to the .................. (sharing/transfer) of electrons. (ii) Electrovalent compounds have a .....................(low/high) boiling point. (iii) A molecule of ................... contains a triple bond. (hydrogen, ammonia,nitrogen) (iv) Across a period, the ionization potential .......................(increases, decreases, remains same.) (v) Down the group, electron affinity ................. (increases, decreases, remains same). (e) (i) Calculate the volume of 320 g of SO2 at stp. (Atomic mass : S = 32 and O = 16) (ii) State Gay-Lussaic s Law of combining volumes. (iii) Calculate the volume of oxygen required for the complete combustion of 8.8g of propane (C3 H8). (Atomic mass : C = 14, O = 16, H = 1, Molar Volume = 22.4 dm3 at stp) (f) Choose the correct answer from the options given below : (i) This metal is a liquid at room temperature. (a) Potassium (b) Zinc (c) Gold (d) Mercury (ii) Hydroxide of this metal is soluble in sodium hydroxide solution. (a) Magnesium (b) Lead (c) Silver (d) Copper (iii) In the periodic table alkali metals are placed in the group .............. (a) 1 (b) 11 (c) 17 (d) 18 (iv) Hydrogen chloride gas being highly soluble in water is dried by : (a) Anhydrous calcium chloride (b) Phosphorous penta oxide (c) Quick lime (d) Concentrated sulphuric acid. (v) The brown ring test is used for detection of : (a) CO2 3 (b) NO 3 (c) SO23 (d) Cl (vi) When dilute sulphuric acid reacts with iron sulphide, the gas evolved is .................. (a) Hydrogen sulphide (b) Sulphur dioxide (c) Sulphur trioxide (d) Vapour of sulphuric acid. (vii) The functional group present in acetic acid is : (a) Ketonic C=O Ch- 138 2011 (b) Hydroxyl OH (c) Aldehydic CHO (d) Carboxyl COOH (viii) The unsaturated hydrocarbons undergo : (a) a substitution reaction (b) an oxidation reaction (c) an addition reaction (d) none of the above (ix) The number of C H bonds in ethane molecule are : (a) Four (b) Six (c) Eight (d) Ten (x) Which of the following properties do not match with elements of the halogen family? (a) They have seven electrons in their valence shell. (b) They are highly reactive chemically. (c) They are metallic in nature. (d) They are diatomic in their molecular form. (g) Write the balanced chemical equation for each of the following reactions : (i) Sodium thiosulphate is reacted with dilute hydrochloric acid (ii) Calcium bicarbonate reacts with dilute hydrochloric acid (iii) Dilute sulphuric acid is poured over sodium sulphite (iv) Lead nitrate solution is added to sodium chloride solution (v) Zinc is heated with sodium hydroxide solution. Answer. (a) (i) Barium chloride (ii) Platinum (iii) Coke (iv) Acetylene (v) Bronze (b) (i) On adding ammonium hydroxide in small amount, blue precipitates will appear. On adding ammonium hydroxide in excess, blue precipitates will dissolve forming deep blue solution. CuSO4 + 2 NH4 OH Cu (OH)2 + (NH4)2 SO4 Blue ppt. In excess Cu (OH)2 + (NH4)2 SO4 + 2NH4OH [Cu (NH3)4]SO4 + 4H2O Deep Blue Solution (ii) Black charred residue is observed H 2SO 4 C12 H22O11 Conc. 12C Black charred residue + 11H2O Ch- 139 2011 (iii) Reddish brown gas is evolved Cu + 4HNO3 Cu (NO3)2 + 2H2O + NO2 Reddish brown gas (iv) Pungent, alkaline gas is evolved. Urinals and stables often smell of this gas. 2Al + N2 2AlN [Burning of aluminium] Al (OH)3 + NH3 [Pungent gas] AIN + 3H2O (v) Reddish brown deposits of copper metal are seen. D CuO + CO Cu + CO2 Reddish Brown This is because carbon monoxide (CO) acts as a reducing agent and reduces copper oxide (CuO). (c) (i) Because of two reasons : 1. It initiates the chemical reaction which increases the rate of reaction. 2. Secondly, same amount of acid is recovered at the end of reaction. (ii) Because of ability of carbon to catenate i.e forms straight chain, branched chains or ring like compounds. (iii) Because carbon monoxide is produced in an insufficient supply of air. This gas is extremely poisonous for human beings as it cuts off the oxygen supply by forming carboxyhaemoglobin in the blood. (iv) H Cl H Cl H d+ H Cl Cl d- Pure covalent bond exists between two elements which have similar electronegativities. In hydrogen chloride, chlorine being more electronegative attracts the shared pair of electrons towards itself as a result hydrogen acquires partial positive charge and chlorine gets partial negative charge. Thus, hydrogen chloride can be termed as a polar covalent compound. (v) Oxidising power means to accept electrons. As we move from left to right along a periodic table, the size of element decrease, hold of nucleus increases, incoming electron is accepted easily thus oxidising power of element increases. (d) (i) sharing (ii) high (iii) nitrogen (iv) increases (v) decreases (e) (i) SO2 M.W. = 32 + 16 2 = 64 64 g of SO2 occupy 22.4 litres Ch- 140 2011 1 g of SO2 will occupy 22.4 litres 64 320 g of SO2 will occupy 22.4 320 = 5. 6 20 = 112 litres 64 (ii) It states that Whenever gases react they do so in volumes which bear a simple whole number ratio to one another and to the volumes of gaseous products, all volumes being measured under similar conditions of temperature and pressure. (iii) C3H8 + 5O2 3CO2 + 4 H2O M.W. of C3 H8 = 12 3 + 8 = 44 Volume of 5O2 = 5 22.4 = 112 litres 44 g of propane requires = 112 litres of oxygen 1 g of propane requires = 112 litres 44 8.8 g of propane requires = 112 8.8 =112 .2 = 22.4 litres 44 (f) (i) (iv) (vii) (x) D D D C (ii) B (v) B (viii) C (g) (i) Na2 S2O3 + 2HCl 2NaCl + SO2 + S + H2O (iii) A (vi) A (ix) B (ii) Ca (HCO3)2 + 2HCl CaCl2 + 2 H2O + 2 CO2 (iii) Na2SO3 + H2SO4 (dilute) Na2SO4 + H2O + SO2 (iv) Pb (NO3)2 + 2NaCl PbCl2 + 2NaNO3 (v) Zn + 2NaOH Na2 ZnO2 + H2 SECTION - II (40 Marks) (Attempt any Four Question ) Question 2. (a) Differentiate between electrical conductivity of copper sulphate solution and copper metal. [3] (b) Sodium hydroxide solution is added to the solutions containing the ions mentioned in List X. List Y gives the details of the precipitate. Match the ions with their coloured precipitates. [3] List X List Y i. Pb2+ A. Reddish brown ii. Fe 2+ B. White insoluble in excess 2+ iii. Zn C. Dirty green Ch- 141 2011 3+ iv. Fe D. White soluble in excess 2+ v. Cu E. White soluble in excess 2+ vi. Ca F. Blue (c) During the electrolysis of copper (II) sulphate solution using platinum as cathode carbon as anode : (i) What do you observe as the cathode and at the anode? (ii) What change is noticed in the electrolyte? (iii) Write the reactions at the cathode and at the anode. Answer. (a) 1. 2. 3. 4. and [1] [1] [2] Electrical conductivity of copper sulphate solutions Electrical conductivity of copper metal Flow of electricity takes place in the molten or dissolved state. Flow of electricity is due to the movement of ions. There is chemical decomposition of the copper sulphate solution. The electrical conductivity increases with increase in temperature. Flow of electricity takes place in the solid state. Flow of electricity is due to the movement of electrons. There is no chemical decomposition. The electrical conductivity decreases with the increase in temperature. Pb2+ White soluble in excess Fe2+ Dirty green Zn2+ White soluble in excess Fe3+ Reddish brown Cu2+ Blue Ca2+ White insoluble in excess. Cathode : Reddish brown deposition of copper occurs at cathode. Anode : Colourless gas is evolved at anode. (ii) On prolonged electrolysis, the blue electrolyte turns colourless. (iii) Cathode : Cu2+ + 2e Cu Anode : OH 1e OH (b) (i) (ii) (iii) (iv) (v) (vi) (c) (i) 4OH 2H2O + O2 Question 3. (a) Answer the following questions : (i) Name a metal which is found abundantly in the earth s crust. (ii) What is the difference between calcination and roasting? (iii) Name the process used for the enrichment of sulphide ore. Ch- 142 2011 (iv) Write the chemical formulae of one main ore of iron and aluminium. (v) Write the constituents of electrolyte for the extraction of aluminium. [5] (b) The diagram shows an experimental set up for the laboratory preparation of a pungent smelling gas. The gas is alkaline in nature. (i) (ii) (iii) (iv) (v) Answer. (a) (i) (ii) Name the gas collected in the jar. Write the balanced equation for the above preparation. How is the gas being collected? Name the drying agent used. How will you find that the jar is full of gas? Aluminium Roasting (i) Ore is heated in the presence of air. (ii) Used generally for sulphide ores. Hence SO2 gas is given off. 2ZnS+ 3O2 2ZnO + 2SO2 (iii) Volatile impurities are removed as oxides. Calcination Ore is heated in the absence of air. Used generally for carbonate ores. Hence, CO2 gas is given off. ZnCO3 ZnO + CO2. Moisture, organic impurities and volatile impurities are removed. (iii) Froth floatation process (iv) Iron : Haematite Fe2O3 Aluminium : Bauxite Al2O3.2H2O (v) Constituents of electroylte for the extraction of aluminium Pure molten alumina 20% Cryolite 60% Fluorspar 20% [5] Ch- 143 2011 (b) (i) Ammonia (NH3) (ii) NH4 Cl + Ca (OH)2 CaCl2 + 2H2O + 2NH3 (iii) Downward displacement of air (iv) Quick lime (CaO) (v) Bring a rod dipped in HCl near it. Dense white fumes of ammonium chloride will be formed. [3] Question 4. (a) An organic compound with vapour density = 94 contains C = 12.67%, H = 2.13%, and Br = 85.11%. Find the molecular formula. [Atomic mass : C = 12, H = 1, Br = 80] [3] (b) Calculate the mass of : (i) 1022 atoms of sulphur. (ii) 0.1 mole of carbon dioxide. [Atomic mass : S = 32, C = 12 and O = 16 and Avogadro s Number = 6 1023] [2] (c) In the laboratory preparation of hydrochloric acid, HCl gas is dissolved in water. (i) Draw a diagram to show the arrangement used for the absorption of HCl in water. (ii) Why is such an arrangement necessary? Give two reasons. (iii) Write the chemical equations for the laboratory preparation of HCl gas when the reactants are : (a) below 200 C (b) above 200 C [5] Answer. (a) Element Symbol Atomic No. Percentage Relative no. of Atoms Simplest ratio Carbon C 12 12.67 12.67 = 1.055 12 1.055 =1 1.055 Hydrogen H 1 2.13 2.13 = 2.13 1 2.13 =2 1.055 Bromine Br 80 85.11 85.11 = 1.0638 80 1.0638 =1 1.055 E. F. = CH2 Br Given V.D. + = 94 Molecular mass = 2 V.D. = 2 94 = 188 M.F.M = (E.F.M)n 188 = (94)n n= 188 =2 94 Ch- 144 2011 Molecular formula = (Empirical formula) n = (CH2Br) 2 = C2H4Br2 (b) (i) 6. 022 1023 atoms of sulphur weight = 32 1 atom of sulphur weigh = 32 6.022 10 23 1022 atoms of sulphur weigh = 32 6.022 10 23 1022 = 0.531 g (iii) 1 mole of CO2 weigh = 44 g 0.1 mole of CO2 weigh = 44 0.1 = 4.4 g (c) (i) HCl gas Funnel arrangement H2 O Funnel arrangement used for absorption of HCl in water. (ii) Two reasons for the use of funnel arrangement are : Prevents back suction of water into the flask. Provides a large surface area for the absorption of the gas. (iii) (A) Below 200 C 200 C NaCl + H2SO4 < NaHSO4 + HCl (B) Above 200 C 200 C 2 NaCl + H2SO4 > Na2SO4 + HCl Question 5. (a) Choose the correct word/phrase from within the brackets to complete the following sentences : (i) The catalyst used for conversion of ethene to ethane is commonly......... . (nickel/ iron/cobalt) (ii) When acetaldehyde is oxidized with acidified potassium dichromate, it forms ....... (ester/ethanol/acetic acid) (iii) Ethanoic acid reacts with ethanol in presence of concentracted H 2 SO4, so as to form a compound and water. The chemical reaction which takes place is called.... . (dehydration/hydrogenation/esterification) Ch- 145 2011 (iv) Write the equation for the reaction taking place between 1, 2 - dibromoethane and alcoholic potassium hydroxide. (v) The product formed when ethene gas reacts with water in the presence of sulphuric acid is..... (ethanol/ethanal/ethanoic acid) [5] (b) Write balanced chemical equations for the following : (i) Monochloro ethane is hydrolysed with aqueous KOH. (ii) A mixture of soda lime and sodium acetate is heated. (iii) Ethanol under high pressure and low temperature is treated with acidified potassium dichromate. (iv) Water is added to calcium carbide. (v) Ethanol reacts with sodium at room temperature. Answer. (a) (i) Nickel (ii) Acetic acid (iii) Esterification (iv) CH2- CH2 + 2 KOH 2KBr + CH CH + 2H2O | | Acetylene Br Br 1 , 2- dibromo ethane (v) Ethanol (b) (i) CH3 CH2 Cl + KOH(aq) CH3 CH2 OH + KCl Monochloro ethane Ethanol (ii) CH3 COONa + NaOH CaO Na2 CO3 + CH4 Sodium Ethanoate Methane 2[O] (iii) CH3 CH2 OH Ethanol K2Cr2O7 / H2SO4 CH3 COOH + H2O Ethanoic acid (iv) CaC2 + 2H2O Ca (OH)2 + CH CH Calcium carbide Acetylene (v) 2C2H5 OH + 2Na 2 C2 H5 ONa + H2 Ethanol Sodium ethoxide Question 6. (a) (i) With the help of equations, give an outline for the manufacture of sulphuric acid by the contact process. (ii) What property of sulphuric acid is shown by the reaction of concentrate sulphuric acid when heated with (a) Potassium nitrate (b) Carbon? [5] Ch- 146 2011 (b) (i) What is the special feature of the apparatus that is used in the laboratory preparation of nitric acid? [2] (c) Write balanced chemical equations for the following : (i) Chlorine reacts with excess of ammonia. (ii) Ferric hydroxide reacts with nitric acid. (iii) Zinc oxide dissolves in sodium hydroxide. Answer. (a) (i) Contact process : Sulphur or Pyrite Burner S + O2 SO2 2Fe2O3 + 8SO2 4 Fe S2 + 11O2 Contact Tower 2SO2 + O2 450 C V 2O5 / K2O Absorption Tower SO3 + H2 SO4 2SO3 H2 S2O7 Oleum Dilution Tank H2S2O7 + H2O 2 H2 SO4 (ii) (A) It behaves as a non volatile acid and helps in the production of a volatile acid. 200 C KNO3 + H2SO4 < NaHSO4 + HNO3 Non volatile acid Voolatile acid (B) It behaves as an oxidising agent and oxidises carbon to carbon dioxide CO2 + 2H2O + 2SO2 (b) (i) All glass apparatus is used because the vapours of nitric acid are corrosive and destroy materials like rubber and cork. (ii) The reaction mixture is not heated beyond 200 C because at higher temperature : The nitric acid would decompose : C + 2H2 SO4 4NO2 + 2H2O + O2 The residue, sodium sulphate or potassium sulphate, forms a hard crust that sticks to the glass. Hence, its removal becomes difficult. 4 HNO3 (c) (i) 8 NH3 (excess) + 3Cl2 N2 + 6NH4 Cl Fe (NO3)3 + 3H2O Na2 ZnO2 + H2O (ii) Fe (OH)3 + 3HNO3 (iii) ZnO + 2NaOH Question 7. (a) (i) Give the number of the group and the period, of the element having three shells with three electrons in valence shell. Ch- 147 2011 (ii) By drawing an electron dot diagram, show the lone pair effect leading to the formation of ammonium ion from ammonia gas and hydrogen ion. (iii) What happens to the crystals of washing soda when exposed to air? Name the phenomenon exhibited. [5] (b) Name the method used for preparation of the following salts from the list given below: (i) Sodium nitrate (ii) Iron (III) chloride (iii) Lead chloride (iv) Zinc sulphate (v) Sodium hydrogen sulphate. List : (a) Simple displacement (b) Neutralization (c) Decomposition by acid (d) Double decomposition (e) Direct synthesis Answer. (a) (i) If three shells element belongs to third period. If three valence electrons element belongs to 13 group. (ii) H H+ + 1e 1 Proton 1 Electron 1 Proton 0 Electron [H+ ion is also known as proton] H H N H + H H H+ + H N H H + H N H Ammonia has one lone pair of electrons which is donated to hydrogen atom forming a co-ordinate bond. The arrow represents a co-ordinate bond. The arrow points from the donor to the receptor atom. (iii) It loses its water of crystallisation and becomes amorphous. This phenomenon is known as efflorescence. H D Na2CO3.10H2O Na2CO3 + 10H2O Washing soda (b) (i) B (iii) D (v) C Sodium carbonate (ii) E (iv) A ICSE QUESTION PAPER-2012 (SOLVED) PAPER 2 (CHEMISTRY) (One hour and A half) Answer to this Paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the Question Paper. The time given at the head of this paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. SECTION - I (40 MARKS) (Attempt all questions from this Section) Question 1. (a) Name the gas in each of the following : (i) The gas evolved on reaction of Aluminium with boiling concentrated caustic alkali solution. (ii) The gas produced when excess ammonia reacts with chlorine. (iii) A gas which turns acidified potassium dichromate clear green. (iv) The gas produced when copper reacts with concentrated nitric acid. (v) The gas produced on reaction of dilute sulphuric acid with a metallic sulphide.[5] (b) State one observation for each of the following : (i) Excess ammonium hydroxide solution is added to lead nitrate solution. (ii) Bromine vapours are passed into a solution of ethyne in carbon tetrachloride. (iii) A zinc granule is added to copper sulphate solution. (iv) Zinc nitrate crystals are strongly heated. (v) Sodium hydroxide solution is added to ferric chloride solution at first a little and then in excess. [5] (c) Some word/words are missing in the following statements. You are required to rewrite the statements in the correct form using the appropraite word/words : (i) Ethyl alcohol is dehydrated by sulphuric acid at a temperature of about 170 C. (ii) Aqua regia contains one part by volume of nitric acid and three parts by volume of hydrochloric acid. (iii) Magnesium nitride reacts with water to liberate ammonia. (iv) Cations migrate during electrolysis. (v) Magnesium reacts with nitric acid to liberate hydrogen gas. [5] (d) Choose the correct answer from the options given below : Ch- 148 2012 Ch- 149 (i) (e) (f) (g) (h) 2012 An element in period-3 whose electron affinity is zero. (A) Neon (B) Sulphur (C) Sodium (D) Argon (ii) An alkaline earth metal. (A) Potassium (B) Calcium (C) Lead (D) Copper (iii) The vapour density of carbon dioxide [C = 12, O = 16] (A) 32 (B) 16 (C) 44 (D) 22 (iv) Identify the weak electrolyte from the following : (A) Sodium Chloride solution (B) Dilute Hydrochloric acid (C) Dilute Sulphuric acid (D) Aqueous acetic acid. (v) Which of the following metallic oxides cannot be reduced by normal reducing agents ? (A) Magnesium oxide (B) Copper(II) oxide (C) Zinc oxide (D) Iron(III) oxide [5] Match the following : Column A Column B 1. Acid salt A. Ferrous ammonium sulphate 2. Double salt B. Contains only ions 3. Ammonium hydroxide solution C. Sodium hydrogen sulphate 4. Dilute hydrochloric acid D. Contains only molecules 5. Carbon tetrachloride E. Contains ions and molecules [5] Give the structural formula for the following : (i) Methanoic acid (ii) Ethanal (iii) Ethyne (iv) Acetone (v) 2-methyl propane. [5] Concentrated nitric acid oxidises phosphorus to phosphoric acid according to the following equation : P + 5HNO3 (conc.) H3PO4 + H2O + 5NO2 If 9.3g of phosphorus was used in the reaction, calculate : (i) Number of moles of phosphorus taken. [1] (ii) The mass of phosphoric acid formed. [2] (iii) The volume of nitrogen dioxide produced at STP. [H = 1, N = 14, P = 31, O = 16] [2] Give reasons for the following : (i) Iron is rendered passive with fuming nitric acid. (ii) An aqueous solution of sodium chloride conducts electricity. Ch- 150 (iii) (iv) (v) Answer. (a) (i) (iii) (v) (b) (i) (ii) (iii) (iv) (v) (c) (i) (ii) (iii) (iv) (v) (d) (i) (iii) (v) (e) 1. 2. 3. 4. 5. (f) (i) (iii) (v) 2012 Ionisation potential of the element increases across a period. Alkali metals are good reducing agents. Hydrogen chloride gas cannot be dried over quick lime. Hydrogen gas (ii) Nitrogen Sulphur dioxide (iv) Nitrogen dioxide Hydrogen sulphide White ppt. insoluble in excess ammonium hydroxide. Ethyne decolorizes the colour of bromine solution. the blue colour of copper sulphate solution discharge. Reddish brown gas is evolved. Reddish brown precipitate is formed which in insoluble in excess of NaOH. To give ethane and water Concentrated nitric acid Concentrated hydrochloric acid Annomia gas Cation migrates towards cathode during electrolysis Dilute nitric acid (D) Argon (ii) (B) Calcium (D) 22 (iv) (D) Aqueous acetic acid (A) Magnesium oxide Column A Column B Acid salt C. Sodium hydrogen sulphate Double salt A. Ferrous ammonium sulphate Ammonium hydroxide solution E. Contains ions and molecules Dilute hydrochloric acid B. Contains only ions Carbon tetrachloride D. Contains only molecules HCOOH (ii) CH3CHO CH CH (iv) CH3COCH3 CH3 CH CH3 CH3 (g) Given, P + 5HNO3 (conc.) (i) H3PO4 + H2O + 5NO2 Number of moles of phosphorous taken = 9.3 = 0.3 mole 31 (ii) 1 mole of phosphorous gives = 98gm of phosphoric acid So, 0.3 mole of phosphorous gives = (0.3 98gm) of phosphoric acid [5] Ch- 151 (iii) (h) (i) (ii) (iii) (iv) (v) 2012 = 29.4gm of phosphoric acid 1 moles of phosphoric gives = 112L of NO2 gas at STP So, 0.3 moles of phosphorous gives = (112 0.3)L of NO2 gas at STP = 33.6L of NO2 gas at STP Due to the formation of oxide film on its surface. Due to the presence of free Na+ and Cl ion. Because the atomic radius decreases across a period. Due to this, attraction between the nucleus and electron increases, this result in increase in the ionization potential. Alkali metals are good reducing agents because alkali metals have one valence electron which they lose to attain stability. Hence, they themselves undergo oxidation causing reduction of others and are good reducing agents. Because HCl undergo chemical reaction with quick lime. CaO + 2HCl CaCl2 + H2O SECTION - II (40 MARKS) (Attempt any four questions from this Section) Question 2. (a) Some properties of sulphuric acid are listed below. Choose the role played by sulphuric acid as A, B, C, or D which is responsible for the reactions (i) to (v). Some role/s may be repeated. A. Dilute acid B. Dehydrating agent C. Non-volatile acid (d) Oxidising agent H 2SO 4 CuSO4 5H2O conc. CuSO4 + 5H2O (ii) S + H2SO4 (conc.) 3SO2 + 2H2O (i) 200 C (iii) NaNO3 + H2SO4 (conc.) < NaHSO4 + HCl (iv) MgO + H2SO4 MgSO4 + H2O (v) Zn + 2H2SO4 (conc.) ZnSO4 + SO2 + 2H2O (b) Give balanced equations for the following reactions : (i) Dilute nitric acid and Copper carbonate. (ii) Concentrated hydrochloric acid and Potassium permanganate solution. (iii) Ammonia and Oxygen in the presence of a catalyst. (iv) Silver nitrate solution and Sodium chloride solution. (v) Zinc sulphide and Dilute sulphuric acid. Answer. (a) (i) B : Dehydrating agent (ii) D : Oxidising agent (iii) C : Non-volatile acid (iv) A : Dilute acid (v) D : Oxidising agent [5] [5] Ch- 152 (b) (i) 2012 CuCO3 + dil. 2HNO3 Cu (NO3)2 + H2O = CO2 D (ii) 16 HCl (conc.) + 2KMnO4 2KCl + 2MnCl2 + 5Cl2 + 8H2O (iii) 4NH3 + 5O2 Pt 800 C 4NO + 6H2O (iv) AgNO3 (aq) + NaCl (aq) 2NH3 + 5 O 2 2 Pt 800 C 2NO + 3H2O + D AgCl + NaNO3 (aq) (v) ZnS + H2 SO4 (dil.) ZnSO4 + H2S Question 3. (a) Select the correct answer from the list given in brackets : (i) An aqueous electrolyte consists of the ions mentioned in the list, the ion which could be discharged most readily during electrolysis. [Fe2+, Cu2+, Pb2+, H+]. (ii) The metallic electrode which does not take part in an electrolytic reaction. [Cu, Ag, Pt, Ni]. (iii) The ion which is discharged at the anode during the electrolysis of copper sulphate solutions using copper electrodes as anode and cathode. [Cu2+, OH , SO42 , H+]. (iv) When dilute sodium chloride is electrolysed using graphite electrodes, the cation is discharged at the cathode most readily. [Na+, OH , H+, Cl ]. (v) During silver plating of an article using potassium argentocyanide as an electrolyte, the anode material should be [Cu, Ag, Pt, Fe]. [5] (b) Match the properties and uses of alloys in List 1 with the appropriate answer from List 2. List 1 List 2 1. The alloy contains Cu and Zn, is A. Duralumin hard, silvery and is used in decorative articles. 2. It is stronger than Aluminium, B. Brass light and is used in making light tools. 3. It is lustrous, hard, corrosion resistant C. Bronze and used in surgical instruments. 4. Tin lowers the melting point of the D. Stainless stell alloy and is used for soldering purpose. 5. The alloy is hard, brittle, takes up E. Solder polish and is used for making statues. [5] Answer. (a) (i) Cu2+ (ii) Pt 2+ (iii) Cu (iv) H+ (v) Ag (b) List 1 List 2 1. The alloy contains Cu and Zn, is B. Brass Ch- 153 2012 hard, silvery and is used in decorative articles. 2. It is stronger than Aluminium, A. Duralumin D. Stainless steel E. Solder C. Bronze light and is used in making light tools. 3. It is lustrous, hard, corrosion resistant and used in surgical instruments. 4. Tin lowers the melting point of the alloy and is used for soldering purpose. 5. The alloy is hard, brittle, takes up polish and is used for making statues. Question 4. (a) Identify the anion present in the following compounds : (i) Compound X on heating with copper turnings and concentrated sulphuric acid liberates a reddish brown gas. (ii) When a solution of compound Y is treated with silver nitrate solution a white precipitate is obtained which is soluble in excess of ammonium hydroxide solution. (iii) Compound Z which on reacting with dilute sulphuric acid liberates a gas which turns lime waer milky, but the gas has no effect on acidified potassium dichromate solution. (iv) Compound L on reacting with Barium chloride solution gives a white precipitate insoluble in dilute hydrochloric acid or dilute nitric acid. [4] (b) State one chemical test between each of the following pairs : (i) Sodium carbonate and Sodium sulphite (ii) Ferrous nitrate and Lead nitrate (iii) Manganese dioxide and Copper(II) oxide [3] (c) Draw an electron dot diagram to show the structure of hydronium ion. State the type of bonding present in it. [3] Answer. (a) (i) Nitrate ion, NO3 (iii) Carbonate ion, CO 32 (b) (i) (ii) Chloride ion, Cl (iv) sulphate ion, SO42 Sodium carbonate and Sodium sulphate : Add HCl (dil.) to both the compounds and pass the gas liberated through acidified potassium dichromate solution. Na2CO3 + 2HCl 2NaCl + H2O + CO2 (No reaction in potassium dichromate solution) Na2SO3 + 2HCl 2NaCl + H2O + SO2 Ch- 154 2012 (Gas liberated will turn potassium dichromate solution green) (ii) Ferrous nitrate and Lead nitrate : When ammonium hydroxide is added to both the solution, the following reactions take place. Fe(NO3)2 + 2NH4OH Fe(OH)2 + 2NH4NO3 (Dirty green precipitates) Pb (NO3)2 + 2NH4OH Pb (OH)2 + 2NH4NO3 (Chalky white precipitates) Thus, ferrous nitrate will give dirty green precipitates whereas lead nitrate will give chalky white precipitates. (iii) Manganese dioixde and Copper (II) oxide : To both the compounds add conc. HCl and heat, the following observations helps : D MnO2 + 4HCl MnCl2 + 2H2O + Cl2 (conc.) (Greenish yellow gas is liberated) D CuO + HCl CuCl2 + H2O (conc.) (Greenish blue solution) (No gas is liberated but the solution turns bluish) H (c) H O+ H It has coordinate (dative covalent) bonding Question 5. (a) (i) 67.2 litres of hydrogen combines with 44.8 litres of nitrogen to form ammonia under specific conditions as : N2(g) + 3H2(g) 2NH3(g) Calculate the volume of ammonia produced. What is the other substance, if any, that remains in the resultant mixture ? [2] 3 (ii) The mass of 5.6 dm of a certain gas at STP is 12.0 g. Calculate the relative molecular mass of the gas. [2] (iii) Find the total percentage of Magnesium in magnesium nitrate crystals, Mg(NO3)2.6H2O. [Mg = 24; N = 14; O = 16 and H = 1] [2] (b) Refer to the flow chart diagram below and give balanced equations with conditions, if any, for the following conversions A to D. Ch- 155 2012 B Iron(II) chloride Sodium Chloride C Hydrogen Chloride A Ammonium chloride D Lead chloride [4] Answer. (a) Acc. to the equation N2(g) + 3H2(g) (i) 2NH3(g) One mole of nitrogen combine with 3 moles of hydrogen to give 2 moles of ammonia. Therefore, 3 22.4 litre of hydrogen require = 22.4 L of Nitrogen Since, Nitrogen is present in excess amount so it remains in the resultant Mixture and volume of ammonia produced = 2 22.4 L = 44.8 L (ii) 5.6 dm3 of gas weighs = 12.0 g 12.0 gm 1 dm3 of gas weighs = 5 .6 12.0 22.4 gm = 48 gm 22.4 dm3 of gas weighs = 5 .6 Therefore, relative molecular mass of gas = 48 gm (iii) Molar mass of Mg(NO3)2 6H2O = 24 + (14 2) + (16 6) + (1 12) + 6 16 = 256 g Mass percent of Magnesium = (b) [A] NaCl + 24 100 = 9.37% 256 H2SO4 (conc.) below 200 C Sodium chloride [B] 2HCl (dil.) HCl + + Hydrogen chloride + Fe Hydrogen chloride [C] NaHSO4 NH3 Hydrogen chloride [D] Pb(NO3)2 + 2HCl Fe Cl2 + H2 Iron (II) chloride NH4Cl + H2O Ammonium chloride PbCl2 + 2HNO3 HCl Ch- 156 2012 Question 6. (a) Name the following metals : (i) A metal present in cryolite other than sodium. (ii) A metal which is unaffected by dilute or concentrated acids. (iii) A metal present in period 3, group 1 of the periodic table. [3] (b) The following questions are relevant to the extraction of Aluminium : (i) State the reason for addition of caustic alkali to bauxite ore during purification of bauxite. (ii) Give a balanced chemical equation for the above reaction. (iii) Along with cryolite and alumina, another substance is added to the electrolyte mixture. Name the substance and give one reason for the addition. [3] (c) The following questions are based on the preparation of ammonia gas in the laboratory: (i) Explain why ammonium nitrate is not used in the preparation of ammonia. (ii) Name the compound normally used as a drying agent during the process. (iii) How is ammonia gas collected ? (iv) Explain why it is not collected over water. [4] Answer. (a) (i) Aluminium (ii) Gold (iii) Sodium (b) (i) Caustic alkali is added to bauxite ore during extraction as the insoluble part of the bauxite is removed and the alumina component is then precipitated. (ii) The reaction is as follows : Al 2O3 2H2O + 2NaOH 2NaAlO2 + 3H2O (iii) Fluorspar is added along with cryolite and alumina because this helps the mixture to fuse at 950 C instead of 2050 C and the aluminium obtained at this temperature is liquid. (c) (i) Ammonium nitrate does not undergo a reversible sublimation reaction, it melts and then decompses into nitrogen oxide gas and water vapour. Thus it is not used in the preparation of ammonia. NH4NO3 N2O + 2H2O (ii) Calcium oxide (iii) Ammonia is collected in an inverted dry gas jar by downward displacement of air. (iv) It is highly soluble in water and hence cannot be collected by downward displacement of water. Question 7. (a) From the following organic compounds given below, choose one compound in each case which relates to the description (i) to (iv) : [Ethyne, ethanol, acetic acid, ethene, methane] (i) An unsaturated hydrocarbon used for welding purposes. (ii) An organic compound whose functional group is carboxyl. Ch- 157 (iii) (iv) (b) (i) (ii) 2012 A hydrocarbon which on catalytic hydrogennation gives a saturated hydrocarbon. An organic compound used as a thermometric liquid. [4] Why is pure acetic acid known as glacial acetic acid ? Give a chemical equation for the reaction between ethyl alcohol and acetic acid. [2] (c) There are three elements E, F, G with atomic numbers 19, 8 and 17 respectively. (i) Classify the elements as metals and non-metals. [3] (ii) Give the molecular formula of the compound formed between E and G and state the type of chemical bond in this compound. [1] Answer. (a) (i) Ethyne (ii) Acetic acid (iii) Ethene (iv) Ethanol (b) (i) Pure acetic acid is called glacial acetic acid because at a temperature below 16.5 C is solidified as icy mass which floats at the surface of acetic acid as a glacier. (ii) C2H5OH + CH3COOH CH3COOC2H5 + H2O Ethyl alcohol Acetic acid Ethyl propanoate (c) (i) E = Metal, F and G = Non-Metal (ii) The Molecular formula is EG The bonding is electrovalent bond. ICSE QUESTION PAPER-2013 (SOLVED) PAPER 2 (CHEMISTRY) (One hour and A half) Answer to this Paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the Question Paper. The time given at the head of this paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. Section I (40 Marks) Attempt all questions from this Section. Question 1 (a) From the list given below, select the word (s) required to correctly complete blanks (i) to (v) in the following passage. The words from the list are to be used only once. Write the answers as (a) (i), (ii), (iii) and so on. Do not copy the passage. Ans. (ammonia, ammonium, carbonate, carbon dioxide, hydrogen, hydronium, hydroxide, precipitate, salt, water) : (a) A solultion M tuns blue litmus red, so it must contain (i) ............ ions ; another solution O turns red litmus blue and hence, must contain (ii) ......ions. (b) When solution M and O are mixed together, the products will be (iii) ............ and (iv) ............ (c) If a piece of magnesium was put into a solution M, (v) ............ gas would be evolved.(5) Ans. (a) (i) hydronium, (ii) hydroxide (b) (iii) salt, (iv) water (c) (v) hydrogen (b) Identify the gas evolved in the following reactions when : (i) sodium propionate is heated with soda lime. (ii) potassium sulphite is treated with dilute hydrochloric acid. (iii) sulphur is treated with concentrated nitric acid. (iv) a few crystals of KNO3 are heated in a hard glass test tube. (v) concentrated hydrochloric acid is made to react with manganese dioxide. Ans. (i) Ethane gas (iii) Nitrogen dioxide gas Ch- 158 (5) (ii) Sulphur dioxide gas (iv) Oxygen gas 2013 Ch- 159 2013 (v) Chlorine gas (c) State one appropriate observation for each of the following: (i) Concentrated sulphuric acid is added drop wise to a crystal of hydrated copper sulphate. (ii) Copper sulphide is treated with dilute hydrochloric acid. (iii) Excess of chlorine gas is reacted with ammonia gas. (iv) A few drops of dilute hydrochloric acid are added to silver nitrate solution, followed by addition of ammonium hydroxide solution. (v) Electricity is passed through molten lead bromide. (5) Ans. (i) The blue coloured hydrated copper sulphate crystals disintegrate with a hissing sound, giving off steam and leaving behind white residue. (ii) A colourless gas with a smell of rotten eggs is given off and a green coloured solution is formed. (iii) When chlorine gas is in excess as compared to ammonia gas, the ammonia reduces chlorine to hydrochloric acid. (iv) A curdy white precipitate is formed. This precipitate dissolves in excess of ammonium hydroxide to form a colourless solution. (v) The molten lead bromide breaks into lead metal which discharges at cathode and bromine gas which discharged at anode. (d) Give suitable chemical terms for the following : (i) A bond formed by a shared pair of electrons with both electrons coming from the same atom. (ii) A salt formed by incomplete neutralisation of an acid by a base. (iii) A reaction in which hydrogen of an alkane is replaced by a halogen. (iv) A definite number of water molecules bound to some salts. (v) The process in which a substance absorbs moisture from the atmosphere air to become moist, and ultimately dissolves in the absorbed water. Ans. (i) Coordinate bond (iii) Subsitution reaction (ii) Acidic salt (iv) Water of crystallisation (v) Deliquescence (e) Give a chemical test to distinguish between the following pairs of compounds : (i) Sodium chloride solution and sodium nitrate solution. Ans. Add silver nitrate solution to sodium chloride solution and sodium nitrate solution. In case of sodium chloride, a curdy white precipitate is formed. In case of sodium nitrate solution the reaction mixture remains colourless. (ii) Hydrogen chloride gas and hydrogen sulphide gas. Ch- 160 2013 Ans. Moist lead acetate paper turns black in case of hydrogen sulphide gas, but does not change its colour in case of hydrogen chloride gas. (iii) Ethene gas and ethane gas. Ans. To the given gas add few drops of bromine solution in carbon, tetra-chloride. In case of ethene gas, the reddish colour of bromine discharges. However, in case of ethane gas the reddish colour of bromine does not discharge. (iv) Calcium nitrate solution and zinc nitrate solution. Ans. To each of the solution add first ammonium hydroxide solution in small amount and then in excess. In case of calcium nitrate a fine white precipitate is formed, which does not dissolve in excess of sodium hydroxide. In case of zinc nitrate a gelatin like white precipitate is formed which dissolves in excess of sodium hydroxide. (v) Carbon dioxide gas and sulphur dioxide gas. Ans. To each of the gas add few drops of acidified potassium dichromate solution. In case of carbon dioxide no change takes place. In case of sulphur dioxide, potassium dichromate solution turns blue. (f) Choose the most appropriate answer from the following options : (i) Among the period 2 elements, the element which has high electron affinity is (a) Lithium (b) Carbon (c) Chlorine (d) Fluorine Ans. (d) Fluorine has highest electron affinity (ii) Among the following compounds identify the compound that has all three bonds (ionic, covalent and coordinate bond). (a) Ammonia (b) Ammonium chloride (c)Sodium hydroxide (d) Calcium chloride Ans. (b) Ammonium chloride has all the three electronic bonds (iii) Identify the statement that is incorrect about alkanes : (a) They are hydrocarbons. (b) There is single covalent bond between carbon and hydrogen (c) They can undergo both substitution as well as addition reactions (d) On complete combustion they produce carbon dioxide and water. Ans. (c) They can undergo both substitution as well as addition reactions. (iv) Which of these will act as non-electrolyte ? (a) Liquid carbon tetrachloride (b) Acetic acid (c) Sodium hydroxide aqueous solution acid. (d) Potassium chloride aqu. solution. Ans. (a) Liquid carbon tetrachloride is non-electrolyte (v) Which one of the following will not produce an acid when made to react with water ? (a) Carbon monoxide (b) Carbon dioxide (c)Nitrogen dioxide (d) Sulphuric trioxide. Ans. (a) Carbon monoxide gas Ch- 161 2013 (vi) Identify the metallic oxide which is amphoteric in nature : (a) Calcium oxide (b) Barium oxide (c) Zinc oxide (d) Copper (II) oxide Ans. (c) Zinc oxide is an amphoteric oxide (vii) In the given equation identify the role played by concentrated sulphuric acid S + 2H2SO4 3SO2 + 2H2O : (a) Non-volatile acid (b) Oxidising agent (c)Dehydrating agent (d) none of these Ans. (b) Concentrated sulphuric acid acts as oxidising agent (viii) Nitrogen gas can be obtained by heating : (a)Ammonium nitrate (b) Ammonium nitrite (c) Magnesium nitric (d) Ammonium chloride Ans. (b) Ammonium nitrite (ix) Which of the following is not a typical property of an ionic compound ? (a) High melting point (b) Conducts electricity in the molten and in the aqueous solution state (c) They are insoluble in water (d) They exist as oppositely charged ions even in the solid state. Ans. (c) Ionic compounds are generally insoluble in water (x) The metals zinc and tin are present in the alloy : (a) Solder (b) Brass (c) Bronze (d) Duralumin. (10) Ans. Bronze (c) (g) Solve the following : (i) What volume of oxygen is required to burn completely 90 dm3 of butane under similar conditions of temperature and pressure ? 2C4H10 + 13O2 8CO2 + 10H2O Ans. 2C4H10 2Vols. 1 Vol 90 dm3 + 13O2 13Vols. 8CO2 + 10H2O 8 Vols. 13 Vols. 2 13 90 dm3 = 585 dm3 2 Nil (By Gay Lussaic s law) (2) (ii) The vapour density of a gas is 8. What would be the volume occupied by 24.0 g of the gas at STP ? (2) Ans. V.D. of gas = 8 \ Molecular mass of gas = 2 V.D. = 2 8 = 16 \ Gram molecular mass of gas = 16 g Ch- 162 2013 3 16 g of gas at STP occupies = 22.4 dm \ 24 g of gas at STP occupies = 22.4 24 = 33.6 dm3. 16 (iii) A vessel contains X number of molecules of hydrogen gas at a certain temperature and pressure. How many molecules of nitrogen gas would be present in the same vessel under the same conditions of temperature and pressure ? (1) Ans. According to Avogadro s law, equal volumes of all gases under similar conditions of temperature and pressure contain equal number of molecules. Number of molecules of nitrogen = X. SECTION II (40 Marks) Attempt any four questions from this Section Question 2 (a) Group number 2nd period IA 1 Li A R IIA 2 Mg T IIIA 13 D E I IVA 14 VA 15 VIA 16 O H U Si Q VIIA 17 J M 0 18 Ne Y * In this table H does not represent hydrogen. * Some elements are given in their own symbol and position in the periodic table. * While others are shown with a letter. With reference to the table answer the following questions. (i) Identify the most electronegative element. (1) (ii) Identify the most reactive element of group 1. (1) (iii) Identify the element from period 3 with least atomic size. (1) (iv) How many valence electrons are present in Q ? (1) (v) Which element from group 2 would have the least ionization energy ? (1) (vi) Identify the noble gas of the fourth period. (1) (vii) In the compound between A and H what type of bond would be formed and give the molecular formula for the same. (2) Ans. (i) J (ii) R (iii) M (iv) 5 (v) T (vi) Y (vii) A and H form an electrovalent compound and its formula is A2H. (b) Compare the compounds carbon tetrachloride and sodium chloride with regard to solubility in water and electrical conductivity. (2) Ans. Carbon tetrachloride is insoluble in water and is not conducting in nature. Ch- 163 2013 Sodium chloride is soluble in water and is conducting in nature in aqueous state or molten state. Question 3 (a) Choosing the substances from the list given below, write balanced chemical equations for the reactions which would be used in the laboratory to obtain the following salts : Dilute Sulphuric acid Copper Copper (II) carbonate Iron Sodium carbonate Sodium Sodium chloride Zinc nitrate (i) Sodium sulphate (iii) Copper (II) sulphate (ii) Zinc carbonate (iv) Iron (II) sulphate. (4) (b) State two relevant observations for each of the following : (i) Ammonium hydroxide solution is added to copper (II) nitrate solution in small quantities and then in excess. (ii) Ammonium hydroxide solution is added to zinc nitrate solution in minimum quantities and then in excess. (iii) Lead nitrate crystals are heated in a hard glass test tube. Ans. (a) (i) Sodium carbonate and dilute sulphuric acid. Na2CO3 + H2SO4(dil) Na2SO4 + CO2 + H2O (ii) Zinc nitrate and sodium carbonate. Zn(NO3)2(aq) + Na2CO3(aq) ZnCO3(s) + 2NaNO3(aq) (iii) Copper carbonate and dilute sulphuric acid. CuCO3(s) + H2SO4(aq) CuSO4(aq) + H2O(l) + CO2(g) (iv) Iron and dilute sulphuric acid. Fe(s) + H2SO4(aq) FeSO4(aq) + H2(g) (b) (i) With small amount of ammonium hydroxide, a bluish white precipitate is formed. This precipitate dissolves in excess of ammonium hydroxide to form a deep blue solution. (ii) A white gelatin like precipitate is formed which dissolves in excess of ammonium hydroxide. (iii) It gives off a reddish brown gas (NO2). The crystals crumble to form a powdery mass, which is yellow when hot and white when cold. Question 4 (a) Copper sulphate solution is electrolysed using copper electrodes. Study the diagram given below and answer the question that follows: Ch- 164 2013 (i) Which electrode to your left or right is known as the oxidising electrode and why? (2) Ans. Left (anode ; + ve terminal of the battery). It is called the oxidising electrode as anions give their electrons to anode, and thus undergo oxidation. (ii) Write the equation representing the reaction that occurs. (1) Ans. At cathode ( ve terminal of battery ; rich in e ) Cu2+ + 2e Cu At anode (+ ve terminal of battery ; deficient in e ) Cu 2e Cu2+ (iii) State two appropriate observations for the above electrolysis reaction. (2) Ans. The size of anode gradually decreases and that of cathode gradually increases. However, there is no change in the colour of copper sulphate solution. (b) X Y Normal Electronic Configuration 2, 8, 7 2, 8, 2 Nature of oxide Dissolves in water and Very low solubility in water. turns blue litmus red Dissolves in hydrochloric acid Tendency for oxidising Tends to oxidise elements Tends to act as a reducing and reducing reactions and compounds agent Electrical and Thermal Very poor electrical Good Electrical conductor conductivity conductor; Poor thermal Good Thermal conductor conductivity Tendency to form alloys and No tendency to form Forms alloys amalgums alloys Using the information above, complete the following : (i) ............. is the metallic element. (ii) Metal atoms tend to have a maximum of ............. electrons in the outermost energy level. (iii) Non-metallic elements tend to form ............. oxides while metals tend to form ............. oxides. Ch- 165 2013 (iv) Non-metallic elements tend to be ............. conductors of heat and electricity. (v) Metals tend to ............. electrons and act as ............. agents in their reactions with elements and compounds. (5) Ans. (i) Y, (ii) Three (iii) acidic, basic (iv) bad (v) lose, reducing Question 5 a. Give balanced equations for each of the following : (i) Reduction of hot Copper (II) oxide to copper using ammonia gas. Ans. (i) 3CuO + 2NH3 3Cu + 3H2O + N2 (4) (ii) Oxidation of carbon with concentrated nitric acid. Ans. C + 4HNO3 2H2O + 4NO2 + CO2 (iii) Dehydration of concentrated sulphuric acid with sugar crystals Ans. C12H22O11 + 11H2SO4 12C + 11H2O (b) Copy and complete the following table relating to important industrial process : Name of the process Temperature Catalyst Equation for the catalyzed reaction (3) Haber s process Ans. Temperature Catalyst Equation for catalysed reaction 450o C (c) (i) Ans. (ii) Ans. Iron containing N2 + 3H2 450o C Fe + Mo 2NH3 + 22.4 KCal molybdenum The following questions relate to the extraction of aluminium by electrolysis : Name the other aluminium containing compound added to alumina and state its significance. The compound is cryolite [Na3AlF6] The addition of cryolite lowers the melting point of alumina from 2050oC to 950 oC. Furthermore, it increases the electrical conductivity of the molten alumina. Give the equation for the reaction that takes place at the cathode. Al3+ + 3e Al (iii) Explain why is it necessary to renew the anode periodically. Ans. The anode (which is made of carbon) is attacked by nascent oxygen formed due to the discharge of O2 ions and changes to carbon dioxide. As the anode is gradually consumed, it is periodically renewed. Question 6 (a) Give balanced equations for the laboratory preparations of the following organic compounds : (4) (i) A saturated hydrocarbon from iodomethane. Ch- 166 2013 Ans. CH3I + 2H (from Zn/Cu couple) CH4 + HI (ii) An unsaturated hydrocarbon from an alcohol. C Ans. C2H5OH + H2SO4 (conc) 160 C2H4 + H2O (iii) An unsaturated hydrocarbon from calcium carbide. Ans. CaC2 + 2H2O Ca(OH)2 + C2H2 (iv) An alcohol from ethyl bromide. Ans. C2H5Br + KOH (aq) C2H5OH + KBr (b) Give the structural formulae for the following : (i) An isomer of n-butane. (ii) 2-propanol. H H | | Ans. H C C | | HH C H | H H | C H [Iso-butane] | H (3) H OH H |3 1| 2| H C C C H [2-propanol] | | | H H H (iii) Diethyl ether. Ans. H H O H H | | || | | H C C C C C H | | | | H H H H [Di-ethyl ether] (c) Give reasons for the following : (i) Methane does not undergo addition reactions, but ethene does. Ans. All the four covalent bonds between the carbon and hydrogen are fully shared. Thus the hydrogen atom can only be substituted by more reactive atoms or group of atoms. There is no scope of addition of reactive atoms in its molecule. However, in case of ethene there is a double bond between the two carbon atoms. These bonds are under strain and hence can be easily broken by more reactive atoms to form other compounds which are saturated in nature. (ii) Ethyne is more reactive than ethane. Ans. Ethyne has a triple covalent bond ( C C ) between two carbon atoms, whereas ethane has a single covalent bond ( C = C ) between the two carbon atoms. So, the strain in the bonding of ethyne is far more than ethane. This accounts of the reactivity of ethyne as its bonds break more easily than that of ethane. (iii) Hydrocarbons are excellent fuels. (3) Ans. All the constituents of hydrocarbon (carbon and hydrogen) are highly combustible and do Ch- 167 2013 not have any uncombustible content. So, hydrocarbons are excellent fuels. Question 7 (a) O2 is evolved by heating KClO3 using MnO2 as a catalyst 2KClO3 MnO 2 2KCl + 3O2 Ans. (a) 2KClO3 MnO 2 2KCl + 3O2 (5) 2[39+35.5+48] g 2[39+35.5]g 3[22.4] lt 245 g 67.2 lt (i) Calculate the mass of KClO3 required to produce 6.72 litre of O2 at STP. [atomic masses of K = 39, Cl = 35.5, O = 16] (2) Ans. 67.2 lt of oxygen at STP is librated from potassium chlorate = 245 g \ 6.72 lt of oxygen at STP is liberated from potassium chlorate = 245 6.72 = 24.5 g 67.2 (ii) Calculate the number of moles of oxygen present in the above volume and also the number of molecules. (2) Ans. 22.4 lt of oxygen and STP = 1 mole. \ 6.72 lt of oxygen at STP = 6.72 = 0.3 moles 22.4 1 mole of oxygen contains number of molecules = 6 1023 \ 0.3 mole of oxygen contain number of molecules = 6 10 23 0.3 = 1.8 1023 molecules 1 (iii) Calculate the volume occupied by 0.01 mole of CO2 at STP. Ans. 1 mole of carbon dioxide gas at STP occupies = 22.4 lt \ 0.01 mole of carbon dioxide gas at STP occupies = (1) 22.4 0.01 = 0.224 lt = 224 cm3 1 (b) Identify the following substances which are underlined : (i) An alkaline gas which produces dense white fumes when reacted with hydrogen chloride gas. Ans. Ammonia gas. (ii) An acid which is present in vinegar. Ans. Acetic acid or ethanoic acid. (iii) A gas which does not conduct electricity in the liquid state but conducts electricity when dissolved in water. Ans. Hydrogen chloride gas. (iv) A dilute mineral acid which forms a white precipitate when treated with barium chloride solution. Ans. Dilute sulphuric acid. (v) The element which has the highest ionization potential. Ans. Fluorine. ICSE QUESTION PAPER-2014 (SOLVED) PAPER 2 (CHEMISTRY) (Two hours) Answers to this Paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the Question Paper. The time given at the head of this paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. SECTION - I (40 MARKS) (Attempt all questions from this Section) Question 1. (a) Choose the correct answer from the options given below: (i) Ionisation Potential increases over a period from left to right because the: (A) Atomic radius increases and nuclear charge increases (B) Atomic radius decreases and nuclear charge decreases (C) Atomic radius increases and nuclear charge decreases (D) Atomic radius decreases and nuclear charge increases. (ii) A compound X consists of only molecules. Hence X will have: (A) A crystalline hard structure (B) A low melting point and low boiling point (C) An ionic bond (D) A strong force of attraction between its molecules. (iii) When fused lead bromide is electrolysed we observe: (A) a silver grey deposit at anode and a reddish brown deposit at cathode (B) a silver grey deposit at cathode and a reddish brown deposit at anode (C) a silver grey deposit at cathode and reddish brown fumes at anode (D) silver grey fumes at anode and reddish brown fumes at cathode. (iv) The main ore used for the extraction of iron is: (A) Haematite (B) Calamine (C) Bauxite (D) Cryolite (v) Heating an ore in a limited supply of air or in the absence of air at a temperature just below its melting point is known as: (A) smelting (B) ore dressing Ch- 168 2014 Ch- 169 2014 (C) calcination (D) bessemerisation (vi) If an element A belongs to Period 3 and Group II then it will have, (A) 3 shells and 2 valence electrons (B) 2 shells and 3 valence electrons (C) 3 shells and 3 valence electrons (D) 2 shells and 2 valence electrons (vii) The molecule containing a triple co-valent bond is: (A) ammonia (B) methane (C) water (D) nitrogen (viii) The electrolyte used for electroplating an article with silver is: (A) silver nitrate solution (B) silver cyanide solution (C) sodium argentocyanide solution (D) nickel sulphate solution (ix) Aluminium powder is used in thermite welding because, (A) it is a strong reducing agent (B) it is a strong oxidising agent (C) it is corrosion resistant (D) it is a good conductor of heat. (x) The I.U.P.A.C. name of acetylene is, (A) propane (B) propyne (C) ethene (D) ethyne. [10] (b) Fill in the blanks from the choices given within brackets: (i) The basicity of Acetic Acid is (3, 1, 4) (ii) The compound formed when ethanol reacts with sodium is (sodium ethanoate, sodium ethoxide, sodium propanoate) (iii) Quicklime is not used to dry HCl gas because (CaO is alkaline, CaO is acidic, CaO is neutral) (iv) Ammonia gas is collected by (an upward displacement of air, a downward displacement of water, a downward displacement of air) (v) Cold, dilute nitric acid reacts with copper to form (Hydrogen, nitrogen dioxide, nitric oxide). [5] (c) Give one word or phrase for the following: (i) The ratio of the mass of a certain volume of gas to the mass of an equal volume of hydrogen under the same conditions of temperature and pressure. (ii) Formation of ions from molecules. (iii) Electrolytic deposition of a superior metal on a baser metal. O (iv) Hydrocarbons containing a C functional group. (v) The amount of energy released when an atom in the gaseous state accepts an electron to form an anion. [5] (d) Match the options A to E with the statements (i) to (v): A alkynes (i) No. of molecules in 22.4 dm3 of carbon dioxide at s.t.p. Ch- 170 B 2014 alkane (ii) An element with electronic configuration 2, 8, 8, 3 C iron (iii) Cn H2n + 2 23 D 6.023 10 (iv) Cn H2n 2 E metal (v) The metal that forms two types of ions [5] (e) Write balanced equations for the following: (i) Action of heat on a mixture of copper and concentrated nitric acid. (ii) Action of warm water on magnesium nitride. (iii) Action of concentrated sulphuric acid on carbon. (iv) Action of dilute hydrochloric acid on sodium sulphide. (v) Preparation of ethane from sodium propionate. [5] (f) Distinguish between the following pairs of compounds using the test given within brackets: (i) Iron (II) sulphate and iron (III) sulphate (using ammonium hydroxide) (ii) A lead salt and a zinc salt (using excess ammonium hydroxide) (iii) Sodium nitrate and sodium sulphite (using dilute sulphuric acid) (iv) Dilute sulphuric acid and dilute hydrochloric acid (using barium chloride solution) (v) Ethane and ethene (using alkaline potassium permanganate solution) [5] (g) (i) Oxygen oxidises ethyne to carbon dioxide and water as shown by the equation: 2C2H2 + 5O2 4CO2 + 2H2O What volume of ethyne gas at s.t.p. is required to produce 8.4 dm3 of carbon dioxide at s.t.p.? [H = 1, C = 12, O = 16] (ii) A compound made up of two elements X and Y has an empirical formula X2Y. If the atomic weight of X is 10 and that of Y is 5 and the compound has a vapour density 25, find its molecular formula. [5] Answer. (a) (i) (D) Atomic radius decreases and nuclear charge increases. (ii) (B) A low melting point and low boiling point (iii) (C) a silver grey deposit at cathode and reddish brown fumes at anode (iv) (A) Haematite (v) (C) calcination (vi) (A) 3 shells and 2 valence electrons (vii) (D) nitrogen (viii)(C) sodium argentocyanide solution (ix) (A) it is a strong reducing agent (x) (D) ethyne (b) (i) The basicity of Acetic Acid is 1. (ii) The compound formed when ethanol reacts with sodium is sodium ethoxide. (iii) Quicklime is not used to dry HCl gas because CaO is alkaline. (iv) Ammonia gas is collected by a downward displacement of air. (v) Cold, dilute nitric acid reacts with copper to form nitric oxide. Ch- 171 2014 (c) (i) The ratio of the mass of a certain volume of gas to the mass of an equal volume of hydrogen Relative vapour density.. under the same conditions of temperature and pressure (ii) Formation of ions from molecules Ionisation. (iii) Electrolytic deposition of a superior metal on a baser metal Electroplating. O (iv) Hydrocarbons containing a C functional group Ketones. (v) The amount of energy released when an atom in the gaseous state accepts an electron to form an anion Electron Affinity.. (d) A alkynes (iv) Cn H2n 2 B alkane (iii) Cn H2n + 2 C iron (v) The metal that forms two types of ions 23 D 6.023 10 (i) No. of molecules in 22.4 dm3 of carbon dioxide at s.t.p. E metal (ii) An element with electronic configuration 2, 8, 8, 3 (e) (i) Action of heat on a mixture of copper and concentrated nitric acid. Cu + 4HNO3 Cu(NO3)2 + 2H2O + 2NO2 (ii) Action of warm water on magnesium nitride. Mg3N2 + 6H2O 3Mg(OH)2 + 2NH3 (iii) Action of concentrated sulphuric acid on carbon. C + 2H2SO4 CO2 + 2H2O + 2SO2 (iv) Action of dilute hydrochloric acid on sodium sulphide. Na2S + 2HCl 2NaCl + H2S (v) Preparation of ethane from sodium propionate. C2H5 COONa + NaO H C2H6 + Na2CO3 (f) (i) Iron (II) sulphate and iron (III) sulphate (using NH 4OH) Iron (II) sulphate (Fe2+ ion) Fe(OH)2 + (NH4)2 SO4 FeSO4 + 2NH4OH green dirty green ppt. colourless sol. Iron (III) Salt (Fe3+ ion) Fe2(SO4)3 + 6NH4OH 2Fe(OH)3 + 3(NH4)2 SO4 reddish brown ppt. (ii) A lead salt and a zinc salt (using excess NH4OH) Pb(NO3)2 + 2NH4OH Pb(OH)2 + 2NH4NO3 Chalky white ppt. Insoluble in excess of NH4OH ZnSO4 + 2NH4OH Zn(OH)2 + (NH4)2 SO4 White gelatinous ppt. Ch- 172 2014 With excess of NH4OH ppt. dissolves Zn(OH)2 + (NH4)2SO4 + 2NH4OH [Zn(NH3)4] SO4 + 4H2O Tetra amine zinc sulphate (iii) Sodium nitrate and sodium sulphate (using dil. H 2SO4) 200 C NaNO3 + H2SO4 (dil.) < NaHSO4 + HNO3 200 C 2NaNO3 + H2SO4 > Na2SO4 + 2HNO3 Na2SO3 + H2SO4 Na2SO4 + H2O + SO2 Sod. sulphite give SO2 gas but NaNO3 does not (iv) Dilute sulphite acid and dilute hydrochloric acid (using barium chloride solution) BaCl2 + H2SO4 BaSO4 + 2HCl White ppt. BaCl2 + HCl No ppt. formation (v) Ethane and ethene (using alkaline KMnO4) Ethene decolourises the colour of alkaline KMnO 4 but ethane does not (g) (i) 2C2H2 + 5O2 4CO2 + 2H2O 2 vol. 5 vol. 4 vol. 2 vol. 4 vol. of O2 required ethyne = 2 vol. 8.4 dm3 vol. of O2 required ethyne = 2 8 .4 = 4.2 dm3 4 (ii) Empirical formula = X2Y Empirical mass = 2 10 + 5 = 25 25 = n 25 (V.D.) n= 25 =1 25 Moleculer mass = 2 V.D. = 2 25 = 50 Molecules Mass 50 = =2 Emperical Mass 25 Molecular formula = n Empirical formula 2 X2Y = X4Y2 SECTION - II (40 MARKS) (Attempt any four questions from this Section) Question 2. (a) State your observation in each of the following cases: (i) When dilute hydrochloric acid is added to sodium carbonate crystals. (ii) When excess sodium hydroxide is added to calcium nitrate solution. (iii) At the cathode when acidified aqueous copper sulphate solution is electrolyzed with copper electrodes. Ch- 173 2014 (iv) When calcium hydroxide is heated with ammonium chloride crystals. (v) When moist starch iodide paper is introduced into chlorine gas. (b) Study the figure given below and answer the questions that follow: [5] Spray Gay Y Water Dropper Water + Blue Litmus (i) Identify the gas Y. (ii) What property of gas Y does this experiment demonstrate? (iii) Name another gas which has the same property and can be demonstrated through this experiment. [3] (c) (i) Name the other ion formed when ammonia dissolves in water. (ii) Give one test that can be used to detect the presence of the ion produced. [2] Answer. (a) (i) Brisk effervescence of a gas which turns lime water milky. (ii) A chalky white ppt insoluble in excess sodium hydroxide. (iii) Reddish brown deposit. (iv) Gas with a pungent odour evolved. (v) The paper turns blue black. (b) (i) Identify the gas Y It is HCl (Hydrogen chloride) (ii) Property of Y Highly solubility in water (iii) The another gas has same property NH3 (Ammonia) (c) (i) When Ammonia dissolves in water. NH3 + H2O NH4OH NH4OH NH4+ + OH ions formed are ammonium and hydroxyl. (ii) Add copper sulphate solution - pale blue ppt formed or ferrous sulphate solution - dirty green ppt formed Ch- 174 2014 Question 3. (a) State the conditions required for the following reactions to take place: (i) Catalytic hydrogenation of ethyne. (ii) Preparation of ethyne from ethylene dibromide. (iii) Catalytic oxidation of ammonia to nitric oxide. (iv) Any two conditions for the conversion of sulphur dioxide to sulphur trioxide. [5] (b) State the main components of the following alloys: (i) Brass. (ii) Duralumin. (iii) Bronze. [3] (c) Give balanced equations for the following: (i) Laboratory preparation of nitric acid. (ii) Preparation of ethanol from monochloroethane and aq. sodium hydroxide. [2] Answer. (a) (i) Catalytic hydrogenation of ethyne Ni Ni C2H4 C2H2 + H2 C2H6 (200 C) Ethyne convert into ethene and then to ethane and nickel act as catalyst. (ii) Preparation of ethyne from ethylene dibromide. KOH CH CH + 2KBr + 2H2O CH2 CH2 (alc.) Br Br (iii) Catalytic oxidation of ammonia to nitric oxide. C 4NH3 + 5O2 Pt. 800 6H2O + 4NO (iv) Two condition for the conversion of SO 2 to SO3 Catalyst V205, Temp. (450 500) C, Pressure (1 2) atms. (b) Give the main components of following alloys: (i) Brass 60 70% Cu 40 30% Zn (ii) Duralium 95% Al 4% Cu 0.5% Mg 0.5% Mn (iii) Bronze 80% Cu 18% Sn 2% Zn Ch- 175 (c) (i) 2014 Laboratory preparation of nitric acid. 200 C KNO3 + H2SO4 < KHSO4 + HNO3 200 C NaNO3 + H2SO4 < NaHSO4 + HNO3 (ii) Preparation of ethanol from monochloro ethane and aq. sodium hydroxide. CH3CH2Cl + NaOH CH3CH2OH + NaCl Question 4. (a) Give the structural formula of the following: (i) ethanol. (ii) 1-propanal. (iii) ethanoic acid. (iv) 1, 2, dichloroethane. [4] (b) Draw the structure of the stable positive ion formed when an acid dissolves in water. [2] (c) State the inference drawn from the following observations: (i) On carrying out the flame test with a salt P a brick red flame was obtained. What is the cation in P? (ii) A gas Q turns moist lead acetate paper silvery black. Identify the gas Q. (iii) pH of liquid R is 10. What kind of substance is R? (iv) Salt S is prepared by reacting dilute sulphuric acid with copper oxide. Identify S. [4] Answer. (a) Give the structural formula: H H (i) H C C OH Ethanol H H H H O H C C C (ii) 1-propanal H H H O H C C OH (iii) Ethanoic acid H H H H C C H (iv) 1, 2, dichloroethane Cl Cl (b) HCl + H2O H O H H + H3O + Cl H Ch- 176 (c) (i) (ii) (iii) (iv) 2014 2+ Cation in P is Ca . The gas Q is H2S. The substance R is alkaline. The compound or salt S is copper sulphate CuSO 4 CuO + H2SO4 CuSO4 + H2O Question 5. (a) Name the following: (i) The property possessed by metals by which they can be beaten into sheets. (ii) A compound added to lower the fusion temperature of electrolytic bath in extraction of aluminium. (iii) The ore of zinc containing its sulphide. (b) Give one equation each to show the following properties of sulphuric acid: (i) Dehydrating property. (ii) Acidic nature. (iii) As a non-volatile acid. (c) Give balanced chemical equations to prepare the following salts: (i) Lead sulphate from lead carbonate. (ii) Sodium sulphate using dilute sulphuric acid. (iii) Copper chloride using copper carbonate. Answer. (a) (i) Mellability (ii) Cryolite (Na3AlF6) (iii) The ore of zinc containing sulphide ZnS (Zinc Blende). (b) (i) Dehydrating property. 2 SO 4 HCOOH Conc. H CO + H2O (ii) Acidic nature. CuO + H2SO4 CuSO4 + H2O (iii) As a non-volatile acid. NaCl + H2SO4 NaHSO4 + HCl (c) (i) Lead sulphate from lead carbonate. PbCO3 + 2HNO3 Pb(NO3)2 + H2O + CO2 PbSO4 + 2HNO3 Pb(NO3)2 + H2SO4 (ii) Sodium sulphate using dilute sulphuric acid. 200 C 2NaCl + H2SO4 < Na2SO4 + HCl (iii) Copper chloride using copper carbonate. CuCO3 + 2HCl CuCl2 + H2O + CO2 Question 6. (a) (i) State Avogadro s Law. (ii) A cylinder contains 68g of ammonia gas at s.t.p. the [3] [3] [4] Ch- 177 2014 1. 2. 3. What is the volume occupied by this gas? How many moles of ammonia are present in the cylinder? How many molecules of ammonia are present in the cylinder? [N-14, H-1] [4] (b) (i) Why do covalent compounds exist as gases, liquids or soft solids? (ii) Which electrode: anode or cathode is the oxidising electrode? Why? [3] (c) Name the kind of particles present in: (i) Sodium Hydroxide solution. (ii) Carbonic acid. (iii) Sugar solution. [3] Answer. (a) (i) Avogadro s Law states that equal vol. of all gases under similar conditions of temperature and pressure contain the same no. of molecules. (ii) 1. Molecular gram atom wt. of NH3 = 17 gm 17 gm of NH3 has vol. at s.t.p. = 22.4 lt. 2. 68 gm of NH3 has vol. at s.t.p. = 22.4 68 = 89.6 lt. 17 No. of moles in 68 gm of NH3 = 68 = 4 moles. 17 3. No. of molecules of ammonia = 4 6.023 1023 = 24.092 1023 (b) (i) The molecules are held together with weak vander wall s forces. As these forces are weak, so they are gases, liquids or soft solids. (ii) Anode - It takes up the electrons from the anions. (c) (i) Sodium hydroxide sol. only ions (ii) Carbonic acid ions and molecules (iii) Sugar solution only molecules Question 7. (a) An element Z has atomic number 16. Answer the following questions on Z: (i) State the period and group to which Z belongs. (ii) Is Z a metal or a non-metal? (iii) State the formula between Z and Hydrogen. (iv) What kind of a compound is this? [4] (b) M is a metal above hydrogen in the activity series and its oxide has the formula M2O. This oxide when dissolved in water forms the corresponding hydroxide which is a good conductor of electricity. In the above context answer the following: (i) What kind of combination exists between M and O? (ii) How many electrons are there in the outermost shell of M? (iii) Name the group of which M belongs. Ch- 178 (iv) State the reaction taking place at the cathode. (v) Name the product at the anode. Answer. (a) An element Z has atomic number 16 (i) Period 3 group 6 (as E.C. 2, 8, 6) (ii) Z is a non-metal. (iii) Formula between Z and hydrogen is H2Z. (iv) The kind of compound is covalent. (b) (i) Electrovalent combination (ii) One (iii) Alkali metals (iv) Reaction of cathode: M+ + e M (v) Oxygen / O2 2014 [5] ICSE QUESTION PAPER-2015 (SOLVED) PAPER 2 (CHEMISTRY) (Two hours) Answers to this Paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the Question Paper. The time given at the head of this paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. SECTION - I (40 MARKS) (Attempt all questions from this Section) Question 1. (a) Select from the list the gas that matches the description given in each case: [ammonia, ethane, hydrogen chloride, hydrogen sulphide, ethyne] (i) This gas is used as a reducing agent in reducing copper oxide to copper. (ii) This gas produces dense white fumes with ammonia gas. (iii) This gas is used for welding purposes. (iv) This gas is also a saturated hydrocarbon. (v) This gas has a characteristic rotten egg smell. Ans. (i) Ammonia (ii) Hydrogen chloride [5] (iii) Ethyne (iv) Ethane (v) Hydrogen sulphide (b) Choose the most appropriate answer for each of the following: (i) Among the elements given below, the element with the least electronegativity is: (A) Lithium (B) Carbon (C) Boron (D) Fluorine (ii) Identify the statement which does not describe the property of alkenes: (A) They are unsaturated hydrocarbons (B) They decolourise bromine water (C) They can undergo addition as well as substitution reactions (D) They undergo combustion with oxygen forming carbon dioxide and water. (iii) This is not an alloy of copper: (A) Brass (B) Bronze Ch- 179 2015 Ch- 180 2015 (C) Solder (D) Duralumin. (iv) Bonding in this molecule can be understood to involve coordinate bonding. (A) Carbon tetrachloride (B) Hydrogen (C) Hydrogen chloride (D) Ammonium chloride (v) Which of the following would weigh the least? (A) 2 gram atoms of Nitrogen. (B) 1mole of Silver (C) 22.4 litres of oxygen gas at 1 atmospheric pressure and 273K (D) 6.02 . 1023 atoms of carbon. [Atomic masses: Ag=108, N=14, O=16, C=12] [5] Ans. (i) (A) Lithium Lithium is an element with the least electronegativity. (ii) (C) They can undergo addition and substitution reactions. Alkenes do not undergo substitution reaction. (iii) (C) Solder Solder is an alloy of lead and tin. (iv) (D) Ammonium chloride The bond formed between the nitrogen atom in ammonia and the chloride ion is a coordinate bond. (v) (D) 6.02 . 1023 atoms of carbon. (c) Complete the following calculations. Show working for complete credit: (i) Calculate the mass of Calcium that will contain the same number of atom as are present in 3.2 gm of Sulphur. [Atomic masses: S=32, Ca=40] [2] (ii) If 6 litres of hydrogen and 4 litres of chlorine are mixed and exploded and if water is added to the gases formed, find the volume of the residual gas. [2] (iii) If the empirical formula of a compound is CH and it has a vapour density of 13, find the molecular formula of the compound. [1] Ans. (i) Given: Mass of Sulphur = 3.2 gm Solution: 32 g of S 6.022 1023 atoms 3.2 g of S ? 3.2 g of S will contain = 6.022 10 23 3.2 = 6.02 1022 atom 32 40 g of Ca 6.02 1023 atoms Ch- 181 2015 ? = 6.02 1022 atoms Mass of Ca = 40 6.02 10 23 = 4g 6.02 10 22 Mass of calcium = 4 g (ii) 6 litres of hydrogen and 4 litres of chlorine are mixed which results in the formation of 8 litres of HCl gas. When water is added, it results in the formation of hydrochloric acid. So, the amount of gas left is only 2 litres of hydrogen as chlorine acts as a limiting reagent. Therefore, the volume of the residual gas will be 2 litres. (iii) Given: Empirical formula = CH Vapour density = 13 Molecular weight = 2 Vapour density = 2 13 = 26 \ Empirical formula of a compound with molecular mass 26 is CH. n= Molecular mass 26 26 = = =2 Empirical formula (12 + 1) 13 \ Molecular formula of the given compound is 2 (CH) = (CH) 2 = C2H2. (d) State one relevant observation for each of the following: (i) When crystals of copper nitrate are heated in a test tube. (ii) When the gaseous product obtained by dehydration of ethyl alcohol is passed through bromine water. (iii) When hydrogen sulphide gas is passed through lead acetate solution. (iv) When ammonia gas is burnt in an atmosphere of excess oxygen. (v) At the Anode when aqueous copper sulphate solution is electrolysed using copper electrodes. [5] Ans. (i) Reddish brown nitrogen dioxide gas is released and the residue left behind is black copper oxide. (ii) The reddish brown colour of bromine solution gets decolourised. (iii) When hydrogen sulphide gas is passed through lead acetate solution, it forms a black precipitate of lead sulphide. (iv) Ammonia gas burns to form nitrogen gas and steamy fumes of water. Also it burns with greenish yellow flame. (v) The anode slowly dissolves, but the colour of copper sulphate does not change. (e) Identify the acid which matches the following description (i) to (v): Ch- 182 2015 (i) The acid which is used in the preparation of a non-volatile acid. (ii) The acid which produces sugar charcoal from sugar. (iii) The acid which is prepared by catalytic oxidation of ammonia. (iv) The acid on mixing with lead nitrate solution produces a white precipitate which is insoluble even on heating. (v) The acid on mixing with silver nitrate solution produces a white precipitate which is soluble in excess ammonium hydroxide. [5] Ans. (i) Concentrated Nitric Acid (ii) Conc. sulphuric acid (iii) Conc. Nitric acid (iv) Dilute sulphuric acid (v) Dilute hydrochloric acid (f) Give appropriate scientific reasons for the following statements: (i) Zinc oxide can be reduced to zinc by using carbon monoxide, but aluminium oxide cannot be reduced by a reducing agent (ii) Carbon tetrachloride does not conduct electricity. (iii) During electrolysis of molten lead bromide graphite anode is preferred to other electrodes. (iv) The electrical conductivity of acetic acid is less in comparison to the electrical conductivity of dilute sulphuric acid at a given concentration. (v) Electrolysis is of molten lead bromide is considered to be a redox reaction. [5] Ans. (i) The metals in the middle of the activity series like zinc are moderately reactive, and carbon is a good reducing agent because of which zinc oxide gets easily reduced by carbon. Oxides of highly active metals like aluminium have great affinity towards oxygen and so cannot be reduced by carbon. (Note: Error in the question. Zinc oxide can be reduced to zinc metal by using carbon, but aluminium oxide cannot be reduced by a reducing agent.) (ii) Carbon tetrachloride is made of individual covalently bonded molecules, CCl4. In addition, the charged particles are absent in CCl4 which could conduct electricity. So, CCl4 does not conduct electricity. (iii) During the electrolysis of molten lead bromide, a graphite anode is preferred because graphite remains unaffected by the reactive bromine vapours which are released at the anode. (iv) Sulphuric acid is a strong acid compared to acetic acid. A strong acid has more ions than a weak one, and so, its solution will be a better electrical conductor than a weak acid. So, electrical conductivity of acetic acid is less in comparison of electric conductivity of sulphuric acid. (v) In the electrolysis of molten lead bromide, the following reactions take place: At the cathode: Pb2+ (l) + 2e- Pb(l) Ch- 183 2015 At the anode: 2Br (l) Br2 (g) + 2e - - Lead (II) ions (Pb2+) are attracted to the negative electrode, and the Pb2+ ions are forced to accept two electrons. Pb2+ ions are reduced. Bromide ions (Br -) are attracted to the positive electrode and the bromide ions are forced to give away their extra electron to form bromine atoms. Thus, bromide ions are oxidised. So, electrolysis of molten lead bromide is a redox reaction. (g) (i) Give balanced chemical equations for the following conversions A, B and C: C A B Fe FeCl3 FeCO3 Fe(NO3)2 (ii) Differentiate between the terms strong electrolyte and weak electrolyte. (stating any two differences) Ans. [3] [2] (i) A: 2Fe + 3Cl2 Heat 2FeCl3 2FeCl3 + 3Na2CO3 Fe2 (CO3) + 6NaCl C: FeCO3 + 2HNO3 Fe (NO3)2 + H2O + CO2 (ii) Strong Electrolytes Weak Electrolytes Electrolytes which allow a large amount of current to flow through them. The solution of a strong electrolyte contains only free mobile ions. Electrolytes which allow a small amount of current to flow through them. The solution of a weak electrolyte contains ions and molecules. (h) Answer the following questions: (i) Explain the bonding in methane molecule using electron dot structure. [2] (ii) The metal of Group 2 from top to bottom are Be, Mg, Ca, Sr, and Ba. (1) Which one of these elements will form ions most readily and why? (2) State the common feature in the electronic configuration of all these elements. [3] Ans. (i) Formation of methane molecule Non-polar covalent compound: Atom Electronic Nearest To attain stable electronic configuration noble gas configuration of nearest noble gas Carbon 12 Hydrogen 1 6 C [2,4] H [1] 1 Neon [2,8] Carbon needs four electrons to complete the octet Helium [2] Hydrogen needs one electron to complete the duplet One atom of carbon shares four electron pairs, one with each of the four atoms of hydrogen. Ch- 184 2015 Before combination (4 [H] and 1 After combination (CH4 Methane [C] atom) molecule) (ii) (1) In group 2, the atomic size increases down the group. As the atomic size increases, the nuclear charge decreases. Due to this, electrons of the outermost shell lie further away from the nucleus making the removal of electrons easy. So, Ba will form ions readily. (2) All the elements have 2 electrons in their valence shell. SECTION II (40 Marks) Attempt any four questions from this Section Question 2 (a) Arrange the following as per the instructions given in the brackets: (i) Cs, Na, Li, K, Rb (increasing order of metallic character). (ii) Mg, Cl, Na, S, Si (decreasing order of atomic size). (iii) Na, K, Cl, S, Si (increasing order ionization energy) (iv) Cl, F, Br, I (increasing order of electron affinity) [4] Ans. (i) Li < Na < K < Rb < Cs (ii) Na > Mg > Si > S > Cl (iii) K < Na < Si < S < Cl (iv) I < Br < F < Cl (b) Choose the most appropriate answer from the following list of oxides which fit the description. Each answer may be used only once: [SO2, SiO2, Al2O3, MgO, CO, Na2O] (i) A basic oxide. (ii) An oxide which dissolves in water forming an acid. (iii) An amphoteric oxide. (iv) A covalent oxide of a metalloid. Ans. (i) MgO [4] (ii) SO2 Ch- 185 2015 (iii) Al2O3 (iv) SiO2 (c) Element X is a metal with a valency 2, Y is 3 non-metal with a valency 3. (i) Write an equation to show how Y from an ion. (ii) If Y is a diatomic gas, write an equation for the direct combination of X and Y to from a compound. [2] Ans. (i) Y will form an anion by gaining 3 electrons. 3 The equation is given as Y + 3e Y . (ii) The equation for the direct combination of X and Y to form a compound is 3X + Y2 X3Y2 Question 3 (a) Give balanced chemical equations for the following conversions: (i) Ethanoic acid to ethyl ethanoate. (ii) Calcium carbide to ethyne. (iii) Sodium ethanoate to methane. Ans. (i) Ethanoic acid to ethyl ethanoate CH3COOH + C2H5OH Conc. H2SO 4 Warm [3] CH3COOC2H5 + H2O Ethyl ethanoate (ii) CaC2 + 2 H2O Calcium carbide (iii) CH3COONa + NaOH Ca(OH)2 + CH CH Calcium hydroxide CaO o 300 C Na2CO3 + CH4 Methane (b) Using their structural formulae identify the functional group by circling them: (i) Dimethyl ether. (ii) Propanone. Ans. (i) Dimethyl ether (ii) Propanone Ch- 186 2015 (c) Name the following: (i) Process by which ethane is obtained from ethene. (ii) A hydrocarbon which contributes towards the greenhouse effect. (iii) Distinctive reaction that takes place when ethanol is treated with acetic acid. (iv) The property of element by virtue of which atoms of the element can link to each other in the form of a long chain or ring structure. (v) Reaction when an alkyl halide is treated with alcoholic potassium hydroxide. [5] Ans. (i) Hydrogenation (ii) Methane (iii) Esterification (iv) Catenation (v) Dehydrohalogenation Question 4 (a) Identify the anion present in each of the following compounds: (i) A salt M on treatment with concentrated sulphuric acid produces a gas which fumes in moist air and gives dense fumes with ammonia. (ii) A salt D on treatment with dilute sulphuric acid produces a gas which turns lime water milky but has no effect on acidified potassium dichromate solution. (iii) When barium chloride solution is added to salt solution E a white precipitate insoluble in dilute hydrochloric acid is obtained. [3] 2 Ans. (i) Chloride ion (Cl.) (ii) Carbonate ion (CO3 .) 2 (iii) Sulphate ion (SO4 .) (b) The following table shows the tests a student performed on four different aqueous solutions which are X, Y, Z and W. Based on the observations provided, identify the cation present: [4] Chemical test Observation Conclusion To solution X, ammonium A dirty white precipitate is (i) hydroxide is added in minimum formed which dissolves in quantity first and then in excess. To solution Y ammonium hydroxide is added in minimum quantity first and then in excess. To solution W a small quantity of sodium hydroxide solution is added and then in excess. To a salt Z calcium hydroxide solution is added and then heated. excess to form a clear solution A pale blue precipitate is formed which dissolves in excess to form a clear inky blue solution. A white precipitate is formed which remains insoluble. A pungent smelling gas turning moist red litmus paper blue is obtained. (ii) (iii) (iv) Ch- 187 2015 2+ 2+ Ans. (i) Zn (ii) Cu 2+ (iii) Ca (iv) NH4+ (c) Give balanced chemical equations for each of the following: (i) Lab preparation of ammonia using an ammonium salt (ii) Reaction of ammonia with excess chlorine. (iii) Reaction of ammonia with sulphuric acid. Ans. (i) Ammonia is prepared in the laboratory by using ammonium chloride. 2NH4Cl + Ca (OH)2 CaO Ammonium chloride CaCl2 + 2H2O Calcium chloride + [3] 2NH3 Ammonia gas (ii) When ammonia reacts with excess of chlorine, it forms nitrogen trichloride and HCl. NH3 3Cl2 + NCl3 + 3HCl (Nitrogen trichloride) (iii) Ammonia reacts with sulphuric acid to form ammonium sulphate. 2NH3 + H2SO4 (NH4)2SO4 Ammonium sulphate Question 5 (a) Consider the following reaction and based on the reaction answer the questions that follow: (NH 4 ) 2 Cr2 O 7 heat N 2 (g) + 4H 2 O(g) + Cr2 O 3 Calculate: (i) the quantity in moles of (NH4)2Cr2O7 if 63gm of(NH4)2Cr2O7 is heated. (ii) the quantity in moles of nitrogen formed. (iii) the volume in litres or dm3 of N2 evolved at S.T.P. (iv) the mass in grams of Cr2O3 formed at the same time. (Atomic masses: H=1, Ans. The given reaction is as follows: [1] [1] [1] [2] Cr= 52, N=14] (NH 4 ) 2 Cr2 O 7 heat N 2 (g) + 4H 2 O(g) + Cr2 O 3 (i) Given: Weight of (NH4)2Cr2O7 = 63 gm Molar mass of (NH4)2Cr2O7 = (2 14) + (8 1) + (2 52) + (7 16) = 28 + 8 + 104 + 112 = 252 gm 1 mole (NH4)2Cr2O7 = 252 gm 63 = 0.25 moles 252 The quantity of moles of (NH4)2Cr2O7 if 63 gm of (NH4)2Cr2O7 is heated is 0.25 moles. (ii) From the given chemical equation, 1 mole of (NH4)2Cr2O7 produces 1 mole of nitrogen gas. Hence, 63 gm of (NH4)2Cr2O7 = Ch- 188 2015 Hence, 0.25 moles of (NH4)2Cr2O7 can produce 0.25 moles of nitrogen gas. The quantity in moles of nitrogen formed is 0.25 moles. (iii) One mole of an ideal gas at S.T.P. occupies 22.4 litres or dm3. Hence, 0.25 moles of (NH4)2Cr2O7 will occupy 0.25 22.4 = 5.6 litres or dm3. The volume in litres or dm3 of N2 evolved at S.T.P. is 5.6 litres or dm3. (iv) From the given chemical equation, 1 mole of (NH4)2Cr2O7 produces 1 mole of Cr2O3. Hence, 0.25 moles of (NH4)2Cr2O7 will produce 0.25 moles of Cr2O3. Molar mass of Cr2O3 = (2 52) + (3 16) = 104 + 48 = 152 gm 1 mole Cr2O3 = 152 gm Hence, 0.25 moles of Cr2O3 = 0.25 152 = 38 gm The mass in grams of Cr2O3 formed at the same time is 38 gm. (b) (i) For each of the substance listed below, describe the role played in the extraction of aluminium. (1) Cryolite (2) Sodium hydroxide (3) Graphite [3]m 6 (ii) Explain why : (1) In the electrolysis of alumina using the Hall Heroult s Process the electrolyte is covered with powdered coke. (2) Iron sheets are coated with zinc during galvanization. [2] Ans. (i) In the extraction of aluminium, the given compounds play the following roles: (1) Cryolite: It lowers the fusion temperature from 2050 C to 950 C and enhances conductivity. (2) Sodium hydroxide: Two roles are played by sodium hydroxide in the extraction of aluminium. First, finely grinded bauxite (ore of aluminium) is heated under pressure with conc. caustic soda solution (NaOH solution) for 2 8 hours at 140 C to 150 C to produce sodium aluminate. The chemical equation is as follows: Al2O3 2H2O + 2NaOH 2NaAlO2 + 3H2O Second, on diluting sodium aluminate with water and cooling to 50 C, sodium aluminate is hydrolysed to give aluminium hydroxide as precipitate. Here, the impurities dissolve in sodium hydroxide. (3) Graphite: Thick rods of graphite are suspended into the fused electrolyte. They act as an anode where oxygen gas is discharged. (ii) (1) In the electrolysis of alumina using the Hall H roult process, the electrolyte is covered with powdered coke as it reduces heat loss by radiation prevents the burning of the anode (2) Iron sheets are coated with zinc during galvanisation to prevent them from rusting. Question 6 (a) (i) Give balanced chemical equations for the action of sulphuric acid on each of the following: (1) Potassium hydrogen carbonate. (2) Sulphur. (ii) In the contact process for the manufacture of sulphuric acid give the equations for the conversion of sulphur trioxide to sulphuric acid. [2] Ch- 189 2015 Ans. (1) Action of sulphuric acid on potassium hydrogen carbonate 2KHCO3 + H2SO4 K2SO4 + 2H2O + 2CO2 (2) Action of sulphuric acid on sulphur S + 2H2SO4 3SO2 + 2H2O (ii) In the contact process for the manufacture of sulphuric acid, the equations for the conversion of sulphur trioxide to sulphuric acid are SO3 + H2SO4 (conc.) H2S2O7 (oleum or pyrosulphuric acid) H2S2O7 + H2O 2H2SO4 (b) (i) Copy and complete the following table: Anode Purification of copper (ii) Write the equation taking place at the anode. Ans. (i) Anode Purification of copper Impure copper Electrolyte [2] [1] Electrolyte Solution of copper sulphate and dilute sulphuric acid (ii) Equation at the anode: 2+ Cu 2e Cu (c) Explain the following: (i) Dilute nitric acid is generally considered a typical acid but not so in its reaction with metals. (ii) Concentrated nitric add appears yellow when it is left standing in a glass bottle. (iii) An all glass apparatus is used in the laboratory preparation of nitric acid. [3] Ans. (i) Dilute nitric acid is generally considered a typical acid but not in its reaction with metals because the action of nitric acid on metals depends on the temperature and concentration of nitric acid. These conditions are not required in case of hydrochloric acid or sulphuric acid. (ii) Although pure concentrated nitric acid is colourless, it appears yellow when left standing in a glass bottle due to the dissolution of reddish brown nitrogen dioxide gas in the acid. Nitrogen dioxide is produced because of the thermal decomposition of a portion of nitric acid. 4HNO3 2H2O + 4NO2 + O2 (iii) An all-glass apparatus is used in the laboratory preparation of nitric acid because nitric acid vapours corrode rubber and cork. Question 7 (a) The following questions are pertaining to the laboratory preparation of hydrogen chloride gas: (i) Write the equation for its preparation mentioning the condition required. [1] (ii) Name the drying agent used and justify your choice. [2] (iii) State a safety precaution you would take during the preparation of hydrochloric acid. [1] Ch- 190 2015 Ans. (i) The equation for the laboratory preparation of hydrogen chloride gas: 200 o C NaCl + H2SO4 < NaHSO4 + HCl Although it is a reversible reaction, it goes to completion as hydrogen chloride continuously escapes as a gas. The reaction can occur up to the stage of the formation of sodium sulphate on heating above 200 C. o above 200 C NaHSO4 + NaCl Na2SO4 + HCl 424 (ii) The drying agent used in the laboratory preparation of hydrochloric acid is conc.sulphuric acid. Or H2SO4 (iii) Funnel arrangement are to be done as HCl is highly soluble in water and to avoid back suction. Always wear chemical splash goggles, Chemical Resistant Gloves and Chemical Resistant apron in the laboratory during the preperation of Hydrochloric acid. (b) An element L consists of molecules. (i) What type of bonding is present in the particles that make up L? (ii) When L is heated with iron metal, it forms a compound FeL. What chemical term would you use to describe the change undergone by L? [2] Ans. (i) Covalent bonding is observed in atoms which are similar. Hence, covalent bonding is present in the particles which make up element L. (ii) When L is heated with iron metal, it forms a compound FeL. Here, oxidation of Fe and reduction of L occur as follows: Fe Fe2+ + 2e (c) From the list of the following salts choose the salt that most appropriately fits the description given in the following: [AgCl, MgCl2, NaHSO4, PbCO3, ZnCO3, KNO3, Ca(NO3)2] (i) A deliquescent salt. (ii) An insoluble chloride. (iii) On heating, this salt gives a yellow residue when hot and white when cold. (iv) On heating this salt, a brown coloured gas is evolved. Ans. [4] (i) A deliquescent salt = MgCl2 (ii) An insoluble chloride = AgCl (iii) On heating, this salt gives a yellow residue when hot and a white residue when cold = ZnCO 3 (iv) On heating this salt, a brown-coloured gas is evolved = Ca(NO 3)2 ICSE QUESTION PAPER-2016 (SOLVED) PAPER 2 (CHEMISTRY) (Two hours) Answers to this Paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the Question Paper. The time given at the head of this paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. SECTION - I (40 MARKS) (Attempt all questions from this Section) Question 1. (a) Fill in the blanks with the choices given in brackets. [5] (i) Metals are good ............ (oxidizing agents/reducing agents) because they are electron ............ (acceptors / donors). (ii) Electrovalent compounds have ............ (high / low) melting points. (iii) Higher the pH value of a solution, the more ............ (acidic / alkaline) it is. (iv) ............ (AgCl / PbCl2), a white precipitate is soluble in excess NH4OH. (v) Conversion of ethene to ethane is an example of ............ (hydration / hydrogenation). Ans. (i) Metals are good reducing agents. because they are electron donors. (ii) Electrovalent compounds have high melting points. (iii) Higher the pH value of a solution, the more alkaline it is. (iv) AgCl (because of formation of diammine silver chloride), a white precipitate is soluble in excess NH4OH. (v) Conversion of ethene to ethane is an example of hydrogenation. (b) Choose the correct answer from the options given below : [5] (i) An element with the atomic number 19 will most likely combine chemically with the element whose atomic number is : (A) 17 (B) 11 (C) 18 (D) 20 (ii) The ratio between the number of molecules in 2 g of hydrogen and 32 g of oxygen is : (A) 1 : 2 (B) 1 : 0.01 (C) 1 : 1 (D) 0.01 : 1 [Given that H = 1, O = 16] (iii) The two main metals in Bronze are : Ch- 191 2016 Ch- 192 2016 (A) Copper and zinc (B) Copper and lead (C) Copper and nickel (D) Copper and tin (iv) The particles present in strong electrolytes are : (A) only molecules (B) mainly ions (C) ions and molecules (D) only atoms (v) The main of the Fountains Experimeter is to prove that : (A) HCl turns blue litmus red (B) HCl is denser than air (C) HCl is highly soluble in water (D) HCl fumes in moist air. Ans. (i) (A) 17 (ii) (C) 1 : 1 (iii) (D) Copper and tin (iv) (B) mainly ions (v) (C) HCl is highly soluble in water (c) Write balanced chemical equations for each of the following : (i) Action of warm water on AIN. (ii) Action of hot and concentrated Nitric acid on copper. (iii) Action of Hydrochloric acid on sodium bicarbonate. (iv) Action of dilute Sulphuric acid on Sodium Sulphite. (v) Preparation of ethanol from Ethyl Chloride. Ans. (i) [5] AlN + 3H2O Al(OH)3 + NH3 (ii) Cu + 4HNO3 Cu(NO3)2 + 2H2O + 2NO2 (iii) NaHCO3 + HCl NaCl + H2O + CO2 (iv) Na2SO3 + H2SO4 Na2SO4 + H2O + SO2 (v) C2H5Cl + NaOH(aq) C2H5OH + NaCl (d) State your observations when : [5] (i) Dilute Hydrochloric acid is added to Lead nitrate sodium and the mixture is heated. (ii) Barium chloride solution is mixed with Sodium Sulphate Solution. (iii) Concentrated Sulphuric acid is added to Sugar Crystals. (iv) Dilute Hydrochloric acid is added to Copper carbonate. (v) Dilute Hydrochloric acid is added to Sodium thiosulphate. Ans. (i) Pb(NO3)2 + 2HCl (dil) PbCl2 + 2HNO3 Lead chloride (white precipitate) When dilute hydrochloric acid is added to lead nitrate white precipitates of lead chloride are formed. (ii) BaCl2 + Na2SO4 BaSO4 + 2NaCl (White precipitates) Ch- 193 2016 When sodium sulphate is mixed with barium chloride. White coloured precipitates of Barium sulphate are formed. SO 4 (iii) C12H22O11 (s) Conc.H 2 12C (s) + 11 H2O (sugar charcoal Black spongy mass) When conc. sulphuric acid is added to sugar crystals black spongy mass (sugar charcoal) is formed. (iv) CuCO3 + 2HCl CuCl2 + H2O + CO2 Brisk effervescence When dilute hydrochloric acid is added to copper carbonate brisk effervescence due to the liberation of carbon dioxide is observed. (v) Na2S2O3 + 2HCl 2NaCl + H2O + SO2 + S (yellow residue) When dilute hydrochloric acid is added to sodium thiosulphate yellow residue (due to formation of sulphur) is formed and a gas with choking odour is formed. (e) Identify the term/substance in each of the following : [5] (i) The tendency of an atom to attract electrons to itself when combined in a compound. (ii) The method used to separate ore from gangue by preferential wetting. (iii) The catalyst used in the conversion of ethyne to ethane. (iv) The type of reactions alkenes undergo. (v) The electrons present in the outermost shell of an atom. Ans. (i) Electronegativity (ii) Froth flotation process (iii) Nickel or platinum or palladium (iv) Addition reactions (v) Valence electrons (f) (i) A gas of mass 32 gms has a volume of 20 litres at S.T.P. Calculate the gram molecular weight of the gas. [5] (ii) How much Calcium oxide is formed when 82 g of calcium nitrate is heated ? Also find the volume of nitrogendioxide evolved : Ans. (i) 2Ca(NO3)2 2CaO + 4NO2 + O2 (Ca = 40, N = 14, O = 16) 20 litres at S.T.P. weighs equal to 32 g 1 litre at S.T.P. weighs equal to 32 g 20 22.4 litres at S.T.P. Weighs equal to (ii) 32 22.4 = 35.84 g 20 2Ca (NO3)2 2CaO + 2[40 + 2 (14 + 48)] 2(40 + 16) 4NO2 + O2 4Vol. Ch- 194 2016 328 g = 112 g 82 g ? ? 328 g will decompose to form 112 g of CaO 1 g will decompose to form 112 g of CaO 328 112 82 g = 28 g of CaO 328 328 g will decompose to form 4 vol of NO2 328 g will decompose to form 4 22.4 l of NO2 82g will decompose to form 1 g will decompose to form 4 22.4 l of NO2 328 4 22.4 82 328 = 22.4 l of NO2 = 1 Volume of NO2. (g) Match the salts given in Column I with their method of preparation given in Column II : [5] Column I Column II (i) Pb(NO3)2 from PbO (A) Simple displacement (ii) MgCl2 from Mg (B) Titration (iii) FeCl3 from Fe (C) Neutralization (iv) NaNO3 from NaOH (D) Precipitation (v) ZnCO3 from ZnSO4 (E) Combination Ans. Column I Column II (i) Pb(NO3)2 from PbO (C) Neutralization (ii) MgCl2 from Mg (A) Simple displacement (iii) FeCl3 from Fe (E) Combination (iv) NaNO3 from NaOH (B) Titration (v) ZnCO3 from ZnSO4 (D) Precipitation (h) (i) Write the IUPAC names of each of the following : 82 g will decompose to form = H H H 1. H C C C H H H 2. H H C C C C H H H H H 3. H C C O H (ii) Rewrite the following sentences by using the correct symbol > (greater than) or < (less than) in the blanks given : Ch- 195 2016 1. 2. Ans. (i) 1. 3. (ii) 1. The ionization potential of Potassium is ............ that of Sodium. The electronegativity of Iodine is ............ that of Chlorine. prop - 1 - ene 2. but - 2 - yne ethanal < (less than) 2. < (less than) SECTION - II (40 MARKS) (Attempt any four questions from this Section) Question 2. (a) Use the letters only written in the Periodic Table Given below to answer the questions that follow : [4] Periods I II Ans. (b) Ans. (c) III IV V VI VII q GROUPS 1 2 Q 3 R 4 T 5 L E G J ZM (i) State the number of valence electrons in atom J. (ii) Which element shown forms ions with a single negative charge? (iii) Which metallic element is more reactive than R? (iv) Which element has its electrons arranged in four shells? (i) J (5 valence electrons) (ii) M (7 valence electrons) so it forms a uninegative ion (iii) T (iv) T Fill in the blanks by selecting the correct word from the brackets : [2] (i) If an element has a low ionization energy then it is likely to be ............ (metallic / non-metallic). (ii) If an element has seven electrons in its outermost shell then it is likely to have the ............ (largest / smallest) atomic size among all the elements in the same period. (i) If an element has a low ionization energy then it is likely to be metallic. (ii) If an element has seven electrons in its outermost shell then it is likely to have the smallest atomic size among all the elements in the same period. The following table shows the electronic configuration of the elements W, X, Y, Z : Element Electronic Configurations W X Y Z 2,8,1 2,8,7 2,5 1 Answer the following questions based on the table above : (i) What type of Bond is formed between : [2] Ch- 196 2016 1. W and X 2. Y and Z (ii) What is the formula of the compound formed between : 1. X and Z 2. W and X Ans. (i) 1. electrovalent bond 2. covalent bond (ii) 1. Z+1 X-1 Z 2. W+1 X-1 W X X Question 3. (a) Write a balanced chemical equation for each of the following : (i) Burning of ethane in plentiful supply of air. (ii) Action of water on Calcium carbide. (iii) Heating of Ethanol at 170 C in the presence of conc. Sulphuric acid. Ans. (i) C2H6 + [2] [3] 7 O 2CO2 + 3H2O 2 2 2C2H6 + 7O2 4CO2 + 6H2O (ii) CaC2 + 2H2O Ca(OH)2 + C2H2 2 SO 4 (iii) C2H5OH Conc. H C2H4 + H2O ethanol ethylene (b) Give the structural formulae of each of the following : (i) 2-methyl propane (ii) Ethanoic acid (iii) Butan 2 ol Ans. (i) [3] H H H H C C C H H H H C H [2-Methyl propane] H (ii) H H C O C O H H (iii) [ethanoic acid] H H OH H H C C C C H H H H H [butan - 2 - ol] (c) Equation for the reaction when compound A is bubbled through bromine dissolved in carbon tetrachloride is as follows : [2] Ch- 197 2016 A Br2/CCl4 CH2Br CH2Br (i) Draw the structure of A. (ii) State your observationduring this reaction. H C Ans. (i) C H H H CH2 == CH2 + Br2 CCl 4 CH2 CH2 (Orangish Br Br red) 1, 2 dibromo ethane (colourless) (ii) Bromine water turns colourless. (d) Fill in the blanks using the appropriate words given below : [2] (Sulphur dioxide, Nitrogen dioxide, Nitric oxide, Sulphuric acid) (i) Cold, dilute, nitric acid reacts with copper to given ............ . (ii) Hot, concentrated nitric acid reacts with sulphur to form ............ . Ans. (i) Cold, dilute, nitric acid reacts with copper to given nitric oxide. (ii) Hot, concentrated nitric acid reacts with sulphur to form sulphuric acid. Question 4. (a) Identify the gas evolved and give the chemical test in each of the following cases : [2] (i) Dilute hydrochloric acid reacts with sodium sulphuric. (ii) Dilute hydrochloric acid reacts with iron (II) sulphide. Na2SO3 + 2HCl 2NaCl + H2O + SO2 Sulphur dioxide Chemical test : Sulphur dioxide decolorises potassium permanganate solution. (ii) FeS + 2HCl FeCl2 + H2S Hydrogen sulphide Chemical test : Hydrogen sulphide turns lead acetate paper black. (b) State your observations when ammonium hydroxide solution is added drop by drop and then in excess to each of the following solutions : [2] (i) copper sulphate solution (ii) zinc sulphate solution Ans. (i) CuSO4 + 2NH4OH Cu(OH)2 + (NH4)2 SO4 Pale Blue Precipitates Cu(OH)2 + 2(NH4)2SO4 + 2NH4OH [Cu(NH3)4] SO4 + 4H2O Deep blue solution Pale blue precipitates are formed and then these precipitates dissolve in excess of ammonium hydroxide to form deep blue solution. Ans. (i) (ii) ZnSO4 + NH4OH Zn(OH)2 + (NH4)2SO4 White gelatinous Ch- 198 2016 Zn(OH)2 + (NH4)2SO4 + 2NH4OH [Zn(NH3)4]SO4 + 4H2O Colourless When ammonium hydroxide is added drop by drop white gelatinous precipitate of zinc hydroxide is formed and on adding excess of ammonium hydroxide colourless solution is formed. (c) Write equations for the reactions taking place at the two electrodes (mentioning clearly the name of the electrode) during the electrolysis of : [4] (i) Acidified copper sulphate solution with copper electrodes. (ii) Molten lead bromide with inert electrodes. Ans. (i) Dissociation reaction : CuSO4 Cu2+ + SO42 H2O H+ + OH H2SO4 2H+ + SO42 Cations Anions At cathode (negative terminal of battery) Cu2+ + 2e Cu(s) copper metal gets deposited [Reduction] At anode (positive terminal of battery) Cu Cu2+ + 2e Copper metal gets converted into ions [Oxidation] (ii) Dissociation reaction PbBr2 (m) Pb2+ + 2Br Cation Anion Cathode Anode Pb Reduction At cathode (negative terminal of battery) Pb2+ + 2e Pb Lead metal is obtained in molten state At anode (positive terminal of battery) Br le Br Br + Br Br2 Reddish brown vapours of bromine are formed (d) (i) Name the product formed at the anode during the electrolysis of acidified water using platinum electrodes. [2] (ii) Name the metallic ions that should be present in the electrolyte when an article made of copper is to be electroplated with silver. Ans. (i) Hydrogen (ii) Silver ions Question 5. (a) A gas cylinder contains 12 1024 molecules of oxygen gas. [2] Ch- 199 2016 23 If Avogadro s number is 6 10 ; Calculate : (i) the mass of oxygen present in the cylinder. (ii) the volume of oxygen at S.T.P. present in the cylinder. [O = 16] Ans. (i) If 6 1023 = 32 g 1 molecules are present the mass is = 32 6 10 23 32 12 1024 6 10 23 = 32 20 = 640 g 12 1024 molecules are present than the mass = (ii) 32 g 22.4 l at S.T.P.. 1 g will occupy a volume of 22.4 32 22.4 640 = 448 l 32 (b) A gaseous hydrocarbon contains 82.76% of carbon. Given that its vapours density is 29, find its molecular formula. [C = 12, H = 1] [3] Ans. Symbol Percentage Atomic mass Relative ratio Simplest ratio Simplest whole no. C 82.76 12 6.89 6.89/6.89 = 1 2 H 17.24 1 17.24 17.24/6.89 = 2.5 5 E.F. = C2H5 E.F.M. = 12 2 + 5 1 = 24 + 5 = 29 V.D. = 29 M.M. = 2 V.D. = 2 29 = 58 640 g will occupy a volume of = M.M 58 = =2 E.F.M 29 Molecular formula = (C2H5)2 = C4H10 (c) The equations 4NH3 + 5O2 4NO + 6H2O, represents the catalytic oxidation of ammonia. If 100 cm3 of ammonia is used calculate the volume of oxygen required to oxidise the ammonia completely. [3] Ans. 4NH3 + 5O2 4NO + 6H2O 4 Vol 5 Vol 4 Vol 100 cm3 ? 4 vol requires 5 vol n= 1 vol requires 5 4 100 cm3 requires 5 100 = 125 cm3 of O2 4 Ch- 200 2016 (d) By drawing an electron dot diagram show the formation of Ammonium Ion [Atomic No. : N = 7 and H = 1] Ans. N(7) 2, 5 H(1) 1 H N H H H N H + H+ + H H N H H H + H N H H Question 6. (a) Name the gas evolved when the following mixtures are heated : (i) Calcium hydroxide and Ammonium Chloride. (ii) Sodium Nitrite and Ammonium Chloride. Ans. (i) Ammonia (ii) Nitrogen (b) Write balanced chemical equations for each of the following : (i) When excess of ammonia is treated with chlorine. (ii) An equation to illustrate the reducing nature of ammonia. Ans. (i) [2] [2] 8NH3 + 3Cl2 6NH4Cl + N2 (ii) 3CuO + 2NH3 3Cu + N2 + 3H2O (c) A, B, C and D summarize the properties of sulphuric acid depending on whether it is dilute or concentrated. [3] A = Typical acid property B = Non-volatile acid C = Oxidizing agent D = Dehydrating agent Choose the property (A, B, C or D) depending on which is relevant to each of the following : (i) Preparation of Hydrogen chloride gas. (ii) Preparation of Copper sulphate from copper oxide. (iii) Action of conc. Sulphuric acid on Sulphur. Ans. (i) Preparation of Hydrogen chloride gas. B = Non-volatile acid (ii) Preparation of Copper sulphate from copper oxide. A = Typical acid property (iii) Action of conc. Sulphuric acid on Sulphur. C = Oxidizing agent Ch- 201 2016 (d) Give reasons why : [3] (i) Sodium Chloride will conduct electricity only in fused or aqueous solution state. (ii) In the electroplating of an article with silver, the electrolyte sodium argentocyanide solution is preferred over silver nitrate solution. (iii) Although copper is a good conductor of electricity, it is a non-electrolyte. Ans. (i) Sodium chloride is a solid, ionic compound, it has strong electrostatic forces of attraction. Only in the fused or aqueous solution, it forms ions which are capable of conducting electricity. (ii) It is preferred over silver nitrate because the dissociation of AgNO 3 will be very fast and deposit will not be smooth and uniform. (iii) An electrolyte must have free ions which act as charge carriers where as in copper the free electrons act as charge carriers. Question 7. (a) (i) Name the solution used to react the Bauxite as a first step in obtaining pure aluminium oxide, in the Baeyer s process. [5] (ii) Write the equation for the reaction where the aluminum oxide for the electrolytic extraction of aluminum is obtained by heating aluminum hydroxide. (iii) Name the compound added to pure alumina to lower the fusion temperature during the electrolytic reduction of alumina. (iv) Write the equation for the reaction that occurs at the cathode during the extraction of aluminium by electrolysis. (v) Explain why it is preferable to use a number of graphite electrodes as anode instead of a single electrode, during the abvoe electrolysis. Ans. (i) Sodium hydroxide solution D Al2O3 + 3H2O (ii) 2Al (OH)3 1100 C (iii) Cryolite (Na3Al F6) acts as a solvent and lower the fusion temperature from 2050 C to 950 C. (iv) Cathode : (rich in electron) Al3+ + 3e Al (v) It is preferable to use a number of graphite electrodes as anode because anode gets oxidised by the oxygen evolved. Hence, if large number of electrodes are used it will keep the process continuous for a longer time. (b) State what would you observe when : [2] (i) Washing Soda Crystals are exposed to the atmosphere. (ii) The salt ferric chloride is exposed to the atmosphere. Na2CO3.10H2O Na2CO3.H2O + 9H2O It will loose water of crystallisation and become a monohydrate. The appearance will be dull and flaky. (ii) Ferric chloride is a deliquescent substance, thus it will absorb water from atmosphere Ans. (i) Ch- 202 2016 and finally dissolve in that water forming a saturated solution. (c) Identify the cations in each of the following case : [3] (i) NaOH solution when added to the Solution (A) gives a reddish brown precipitate. (ii) NH4OH Solution when added to the Solution (B) gives white ppt. which does not dissolve in excess. (iii) NaOH Solution when added to Solution (C) gives white ppt. which is insoluble in excess. Ans. (i) Fe+3 (ii) Pb2+ 2+ (iii) Ca ICSE QUESTION PAPER-2017 (SOLVED) PAPER 2 (CHEMISTRY) (Two hours) Answers to this Paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the Question Paper. The time given at the head of this paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. SECTION - I (40 MARKS) (Attempt all questions from this Section) Question 1. (a) Fill in the blanks from the choices given in brackets. [5] (i) The energy required to remove an electron from a neutral isolated gaseous atom and convert it into a positively charged gaseous ion is called . (electron affinity, ionisation potential, electronegativity) (ii) The compound that does not have a lone pair of electrons is . (water,, ammonia, carbon tetrachloride) (iii) When a metallic oxide is dissolved in water, the solution formed has a high concentration of ions. (H+, H3O+, OH ) gas. (iv) Potassium sulphite on reacting with hydrochloric acid releases (Cl2, SO2, H2S) (v) The compound formed when ethene reacts with Hydrogen is . (CH4 , C2H6, C3 H8 ) Ans. (i) Ionisation potential (ii) Carbon tetrachloride or CCl4 (iii) OH (iv) SO2 (v) C2 H 6 (b) Choose the correct answer from the options given below : [5] (i) A chloride which forms a precipitate that is soluble in excess of ammonium hydroxide, is: (A) Calcium chloride (B) Ferrous chloride (C) Ferric chloride (D) Copper chloride (ii) If the molecular formula of an organic compounds is C10H18 it is: (A) alkene (B) alkane Ch- 203 2017 Ch- 204 Ans. (c) Ans. (d) 2017 (C) alkyne (D) Not a hydrocarbon (iii) Which of the following is a common characteristic of a covalent compound? (A) high melting point (B) consists of molecules (C) always soluble in water (D) conducts electricity when it is in the molten state (iv) To increase the pH value of a neutral solution, we should add: (A) an acid (B) an acid salt (C) an alkali (D) a salt (v) Anhydrous iron (III) chloride is prepared by: (A) direct combination (B) simple displacement (C) decomposition (D) neutralization (i) (D) copper chloride (ii) (C) alkyne (iii) (B) consists of molecules (iv) (C) an alkali (v) (A) direct combination Identify the substance underlined, in each of the following cases: [5] (i) Cation that does not form a precipitate with ammonium hydroxide but forms one with sodium hydroxide. (ii) The electrolyte used for electroplating an article with silver. (iii) The particles present in a liquid such as kerosene, that is a non-electrolyte. (iv) An organic compound containing COOH functional group. (v) A solid formed by reaction of two gases, one of which is acidic and the other basic in nature. (i) Ca 2+ (ii) sodium silver cyanide solution Na[Ag(CN)2] (iii) Free molecule (iv) carboxylic acid (v) ammonium chloride (NH4Cl) Write a balanced chemical equation for each of the following: [5] (i) Action of cold and dilute nitric acid on copper. (ii) Reaction of ammonia with heated copper oxide. (iii) Preparation of methane from iodomethane. (iv) Action of concentrated sulphuric acid on sulphur. (v) Laboratory preparation of ammonia from ammonium chloride. Ans. (i) 3Cu + 8HNO3 (dil) 3Cu (NO3)2 + 4H2O + 2NO (ii) 3CuO + 2NH3 3Cu + 3H2O + N2 (iii) CH3I + 2[H] Zn/Cu alcohol CH4 + HI Ch- 205 (e) Ans. (f) Ans. 2017 (iv) S + 2H2SO4 (conc.) 3SO2 + 2H2O (v) 2NH4Cl + Ca(OH)2 CaCl2 + 2H2O + 2NH3 State one relevant observation for each of the following reactions: [5] (i) Addition of ethyl alcohol to acetic acid in the presence of concentrated sulphuric acid. (ii) Action of dilute hydrochloric acid on iron (II) sulphide. (iii) Action of sodium hydroxide solution on ferrous sulphate solution. (iv) Burning of ammonia in air. (v) Action of concentrated sulphuric acid on hydrated copper sulphate. (i) Fruit smell evolved (Ether). (ii) H2S evolves with rotten egg smell. (iii) Dirty green ppt [Fe(OH)2] which is insoluble in excess NaOH. (iv) Burns with a green flame producing N2 and H2O. (v) Blue crystal loses its crystalline shape and becomes white amorphous. (i) Draw the structural formula for each of the following: [5] 1. 2, 3 dimethyl butane 2. diethyl ether 3. propanoic acid (ii) From the list of terms given, choose the most appropriate term to match the given description. (calcination, roasting, pulverisation, smelting) 1. Crushing of the ore into a fine powder. 2. Heating of the ore in the absence of air to a high temperature. (i) 1. 2, 3 dimethyl butane H CH3 CH3 H3C CH CH CH3 (4) 2. (3) (2) C H H H Or H C C C C H H (1) H H H H diethyl ether H H C2H5 O C2H5 H H Or H C C O C C H H H 3. Propanoic acid H H O H C C C OH H H H H Ch- 206 2017 (ii) 1. Pulverisation 2. Calcination (g) (i) Calculate the number of gram atoms in 4.6 grams of sodium (Na = 23). [5] (ii) Calculate the percentage of water of crystallization in CuSO4.5H2O (H = 1, O = 16, S = 32, Cu = 64) (iii) A compound of X and Y has the empirical formula XY2. Its vapour density is equal to its empiricial formula weight. Determine its molecular formula. Ans. (i) 23 g of sodium = 1 gram atom 4.6 g of sodium = 1 4.6 = 0.2 gram atom 23 (ii) Molecular mass of CuSO4.5H2O CuSO4 Cu = 64 1 = 64 S = 32 1 = 32 O = 16 4 = 64 160 g \ \ 5H2O H = 1 10 = 10 O = 16 5 = 80 90 g Molecular mas of compound = 160 + 90 = 250 g % of water of crystallization = 90 100 = 36% 250 (ii) Let V.D. of compound = n Molecular mass = 2x Empirical formula weight = x \ Molecular mass n = Empirical formula weight = 2x 2 x \ Molecular formula of the compound = 2(XY2) = X2Y4 (h) Match the atomic number 2, 4, 8, 15, and 19 with each of the following: (i) A solid non-metal belonging to the third period. (ii) A metal of valency 1. (iii) A gaseous element with valency 2. (iv) An element belonging to Group 2. (v) A rare gas. Ans. (i) 15 (ii) 19 (iii) 8 (iv) 4 (v) 2 [5] Ch- 207 2017 SECTION - II (40 MARKS) (Attempt any four questions from this Section) Question 2. (a) Arrange the following as per the instruction given in the brackets: [4] (i) He, Ar, Ne (Increasing order of the number of electron shells) (ii) Na, Li, K (Increasing ionisation energy) (iii) F, Cl, Br (Increasing electronegativity) (iv) Na, K, Li (increasing atomic size) Ans. (i) He, Ne, Ar (ii) K, Na, Li (iii) Br, Cl, F (iv) Li, Na, K (b) State the type of Bonding in the following molecules: [2] (i) Water (ii) Calcium oxide Ans. (i) Water Covalent bond (ii) Calcium oxide Electrovalent bond (c) Answer the following questions: [2] (i) How will you distinguish between ammonium hydroxide and sodium hydroxide using copper sulphate solutions? (ii) How will you distinguish between dilute hydrochloric acid and dilute sulphuric acid using lead nitrate solution? Ans. (i) Using NaOH, it forms blue ppt which is insoluble in excess NaOH. With NH4OH it forms blue ppt which is soluble in excess NH4OH. (ii) Using lead nitrate solution, only HCl will form curdy white ppt and not H2SO4. (d) Identify the salts P and Q from the observations given below: [2] (i) On performing the flame test salt P produces a lilac coloured flame and its solution gives a white precipitate with silver nitrate solution, which is soluble in ammonium hydroxide solution. (ii) When dilute HCl is added to a salt Q, a brisk effervescence is produced and the gas turns lime water milky. When NH4OH solution is added to the above mixture (after adding dilute HCl), it produces a white precipitate which is soluble in excess NH 4 OH solution. Ans. (i) Salt P is potassium chloride (KCl) (ii) Salt Q is zinc carbonate (ZnCO3) Question 3. (a) Draw an electron dot diagram to show the formation of each of the following compounds: [4] (i) Methane (ii) Magnesium chloride [H = 1, C = 6, Mg = 12, Cl = 17] Ans. (i) Methane [H = 1, C = 6] Ch- 208 2017 Hydrogen atom: Z = 1 Configuration: 1 Carbon atom: Z = 6 Configuration: 2, 4 H H H + H + C + H H C H H C H + H H H (ii) Magnesium chloride Mg atom: Z = 12 Configuration: 2, 8, 2 Cl atom: Z = 17 Configuration: 2, 8, 7 ++ Cl + Mg + Cl (Mg) + 2( Cl ) MgCl2 (b) State the observations at the anode and at the cathode during the electrolysis of: [4] (i) fused bromide using graphite electrodes. (ii) copper sulphate solution using copper electrodes. Ans. (i) At cathode, Pb2+ migrate to form silvery grey metallic lead. At anode, Br migrate forming bromide atom and then bromine molecule, ultimately forming bromine vapours. These are Reddish Brown Fumes. (ii) At cathode, Cu2+ ions accept electrons and form neutral copper atom deposition here size of Anode gets decreases. At anode, neither SO42 nor OH , are discharged and copper atoms of the anode lose electrons and enter the solution as copper ions. (c) Select the ion in each case, that would get selectively discharged from the aqueous mixture of the ions listed below: [2] 2 (i) SO4 , NO3 , and OH (ii) Pb2+, Ag+ and Cu2+ Ans. (i) OH (ii) Ag+ Question 4. (a) Certain blank spaces are left in the following table and these are labelled as A, B, C, D and E. Identify each of them. [5] Lab preparation of Reactants used Products formed Drying agent Method of collection (i) HCl gas NaCl + H2SO4 ___A___ conc. H2SO4 ___B___ (ii) NH3 gas ___C___ Mg(OH)2 NH3 ___D___ ___E___ Ch- 209 2017 A NaHSO4 + HCl B Upward displacement of air (ii) C Mg3N2 + H2O D CaO (Calcium oxide) E By downward displacement of air (b) Write balanced chemical equations to show: (i) The oxidizing action of conc. sulphuric acid on carbon. (ii) The behaviour of H2SO4 as an acid when it reacts with magnesium. (iii) The dehydrating property of conc. sulphuric acid with sugar. Ans. (i) C + 2H2SO4 CO2 + 2H2O + SO2 (conc) (ii) Mg + H2SO4 MgSO4 + H2 Ans. (i) (iii) C12H22O11 H 2SO4 (conc) [3] 12C + 11H2O (c) Write balanced chemical equations to show how SO3 is converted to sulphuric acid in the contact process. [2] Ans. SO3 + H2SO4 H2S2O7 H2S2O7 + H2O 2H2SO4 Question 5. (a) (i) Propane burns in air according to the following equation: [4] C3H8 + 5O2 3CO2 + 4H2O. What volume of propane is consumed on using 1000 cm3 of air, considering only 20% of air contains oxygen? (ii) The mass of 11.2 litres of a certain gas at s.t.p. is 24 g. Find gram molecular mass of the gas. Ans. (i) According to the equation C3H8 + 5O2 3CO2 + 4H2O 1 vol : 5 vol : : 3 vol : 4 vol Reacting oxygen in 1000 cm3 of air is 20 1000 = 200 cm3 100 Vol of O2 5 Vol 200 cm3 \ 1 Vol 40 cm3 \ Vol of propane consumed = 1 Vol = 1 40 = 40 cm3 (ii) 11.2 litre of gas 24 g \ 22.4 litre (molar volume) = \ 24 22.4 = 48 g 11.2 Gram molecular mass is 48 g. Ch- 210 2017 (b) A gas cylinder can hold 1 kg of hydrogen at room temperature and pressure: [4] (i) Find the number of moles of hydrogen present. (ii) What weight of CO2 can the cylinder hold under similar conditions of temperature and pressure? (H = 1, C = 12, O = 16) (iii) If the number of molecules of hydrogen in the cylinder is x, calculate the number of CO 2 molecules in the cylinder under the same conditions of temperature and pressure. (iv) State the law that helped you to arrive at the above result. Ans. (i) Molecular mass of hydrogen = 2 1 g 2 g is present in 1 mole \ 1000 g (1 kg) 1 1000 500 moles 2 (ii) Molecular mass of CO2 = 12 + 16 2 = 44 g 1 mole = 44 g \ 500 moles = 44 500 = 22000 g = 22 kg (iii) The number of molecules of CO2 in the cylinder is X. (iv) Avogadro s Law Under same condition of temperature and pressure, equal volumes of gases contain the same number of molecules. (c) Write a balanced chemical equation for the preparation of each of the following salts: [2] (i) Copper carbonate (ii) Ammonium sulphate crystals Ans. (i) CuCl2 + Na2CO3 2NaCl + CuCO3 (ii) (NH4)2CO3 + H2SO4 (NH4)2SO4 + H2O + CO2 Question 6. (a) Give a balanced chemical equation for each of the following: (i) Action of conc. nitric acid on sulphur. (ii) Catalytic oxidation of ammonia. (iii) Laboratory preparation of nitric acid. (iv) Reaction of ammonia with nitric acid. Ans. (i) S + 6HNO3 H2SO4 + 6NO2 + 2H2O (conc) [4] Pt 4NO + 6H2O + D (ii) 4NH3 + 5O2 700 800 C 200 C (iii) KNO3 + H2SO4 < KHSO4 + HNO3 (conc) (iv) NH3 + HNO3 NH4NO3 (b) Identify the term or substance based on the descriptions given below: [4] Ch- 211 2017 (i) Ice like crystals formed on cooling an organic acid sufficiently. (ii) Hydrocarbon containing a triple bond used for welding purposes. (iii) The property by virtue of which the compound has the same molecular formula but different structural formulae. O (iv) The compound formed where two alkyl groups are linked by Ans. (i) Glacial acetic acid (ii) Acetylene (iii) Isomerism (iv) Ketone (c) Give a balanced chemical equation for each of the following: (i) Preparation of ethane from sodium propionate. (ii) Action of alcoholic KOH on bromoethane. Ans. (i) C2H5COONa + NaOH D CaO C group. [2] C2H6 + Na2CO3 (ii) C2H5Br + KOH C2H4 + KBr + H2O alcoholic Question 7. (a) Name the following: [4] (i) The process of coating of iron with zinc. (ii) An alloy of lead and tin that is used in electrical circuits. (iii) An ore of zinc containing its sulphide. (iv) A metal oxide that can be reduced by hydrogen. Ans. (i) Galvanisation (ii) Solder (iii) Zinc sulphide or Zinc blende (ZnS) (iv) CuO (b) Answer the following questions with respect to the electrolytic process in the extraction of aluminum: [3] (i) Identify the components of the electrolyte other than pure alumina and the role played by each. (ii) Explain why powdered coke is sprinkled over the electrolytic mixture. Ans. (i) Cryolite lower fusion temperature. Fluorspar acts as solvent for electrolytic mixture and increase conductivity. (ii) To reduce heat loss by radiation and prevent the burning of carbon anode. (c) Complete the following by selecting the correct option from the choices given: [3] (i) The metal which does not react with water or dilute H2SO4 but reacts with concentrated H2SO4 is . (Al/Cu/Zn/Fe) (ii) The metal whose oxide, which is amphoteric, is reduced to metal by carbon reduction . (Fe/Mg/Pb/Al) (iii) The divalent metal whose oxide is reduced to metal by electrolysis of its fused salt is . (Al/Na/Mg/K) Ans. (i) Cu (ii) Pb (iii) Mg ICSE QUESTION PAPER-2018 (SOLVED) PAPER 2 (CHEMISTRY) (Two hours) Answers to this Paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the Question Paper. The time given at the head of this paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. SECTION - I (40 MARKS) (Attempt all questions from this Section) Question 1. (a) Choose the correct answer from the options given below: [5] (i) The salt solution which does not react with ammonium hydroxide is: (A) Calcium Nitrate (B) Zinc Nitrate (C) Lead Nitrate (D) Copper Nitrate (ii) The organic compound which undergoes substitution reaction is: (A) C 2 H 2 (B) C 2 H 4 (C) C 10 H 18 (D) C 2 H 6 (iii) The electrolysis of acidified water is an example of: (A) Reduction (B) Oxidation (C) Redox reaction (D) Synthesis (iv) The IUPAC name of dimethyl ether is: (A) Ethoxy methane (B) Methoxy methane (C) Methoxy ethane (D) Ethoxy ethane (v) The catalyst used in the Contact Process is: (A) Copper (B) Iron (C) Vanadium pentoxide (D) Manganese dioxide Ans. (i) (A) Calcium Nitrate (ii) (D) C2 H 6 (iii) (C) Redox reaction (iv) (B) Methoxy methane (v) (C) Vanadium pentoxide (b) Give one word or a phrase for the following statements: [5] (i) The energy released when an electron is added to a neutral gaseous isolated Ch- 212 2018 Ch- 213 2018 atom to form a negatively charged ion. (ii) Process of formation of ions from molecules which are not in ionic state. (iii) The tendency of an element to form chains of identical atoms. (iv) The property by which certain hydrated salts, when left exposed to atmosphere, lose their water of crystallization and crumble into powder. (v) The process by which sulphide ore is concentrated. Ans. (i) Electron affinity (ii) Ionisation (iii) Catenation (iv) Efflorescence (v) Froth floatation process. (c) Write a balanced chemical equation for each of the following: [5] (i) Action of concentrated sulphuric acid on carbon. (ii) Reaction of sodium hydroxide solution with iron (III) chloride solution. (iii) Action of heat on aluminium hydroxide. (iv) Reaction of zinc with potassium hydroxide solution. (v) Action of dilute hydrochloric acid on magnesium sulphite. Ans. (i) C + 2H2SO4 2H2O + 2SO2 + CO2 (ii) FeCl3 + 3NaOH Fe(OH)3 + 3NaCl (iii) 2Al(OH)3 Al2O3 + 3H2O (iv) Zn + 2KOH K2ZnO2 + H2O (v) MgSO3 + 2HCl MgCl2 + H2O + SO2 (d) (i) Give the IUPAC name for each of the following: H H H 1. H C O 2. H H C C C OH H H H H H 3. H3C C C CH3 (ii) Write the structural formula of the two isomers of butane. Ans. (i) 1. Methanal 2. Propanol 3. But-2-ene H H H H (ii) H C C C C H H H H H (n-butane) Butane H H H H C C C H H H H C C H (Isobutane) 2 Methyl butane (e) State one relevant observation for each of the following: [5] Ch- 214 (i) (ii) (iii) (iv) (v) Ans. (i) 2018 Lead nitrate solution is treated with sodium hydroxide solution drop wise till it is in excess. At the anode, when molten lead bromide is electrolyzed using graphite electrodes. Lead nitrate solution is mixed with dilute hydrochloric acid and heated. Anhydrous calcium chloride is exposed to air for sometime. Barium chloride solution is slowly added to sodium sulphate solution. Pb(NO3)2 + 2NaOH Pb(OH)2 + 2NaNO3 white precipitate Pb(OH)2 + 2NaOH Na2PbO2 + 2H2O (Soluble) When drop by drop of sodium hydroxide is added, chalky white precipitates appear. These precipitates dissolve in excess of sodium hydroxide forming sodium plumbite. (ii) PbBr 2 Pb2+ + 2Br Cation (Cathode) Anion (Anode) At Anode 2Br 2e 2Br Br + Br Br2 At anode reddish vapours of bromine escape in air from lead bromide. (iii) Pb(NO3)2 + 2HCl PbCl2 + 2HNO3 (white precipitates) White precipitates of lead chloride are formed which are soluble in hot water and insoluble in cold water. (iv) Colourless solution or solid CaCl2 turns into solution. (v) A white ppt is formed. (f) Give a reason for each of the following: [5] (i) Ionic compounds have a high melting point. (ii) Inert gases do not form ions. (iii) Ionisation potential increases across a period, from left to right. (iv) Alkali metals are good reducing agents. (v) Conductivity of dilute hydrochloric acid is greater than that of acetic acid. Ans. (i) Ionic compounds have ions held strongly by electrostatic forces of attraction. These strong forces need more energy to be broken apart. Hence, they have high melting point. (ii) Inert gases do not form ions because they have completely filled octet. They are extremely stable. Hence, they neither loose, nor gain electrons. (iii) As we move from left to right a period, the atomic size decreases due to the increase in nuclear charge thus more energy is required to remove the electron, hence ionisation potential increase. Ch- 215 2018 (iv) Alkali metals have free electrons. They can easily loose electrons to form positive ions. The loss of electron is known as oxidation and the substance/element that lose electrons is said to be reducing agent. Na (II) 2, 8, 1 Reducing agent (g) Ans. (h) Ans. - - 1e + Na 2, 8 Loss of electron Oxidation (v) Hydrochloric acid is a strong acid. It splits to give more hydrogen ions as compared to acetic acid. Hence, conductivity of dilute hydrochloric acid is more than that of acetic acid. Name the gas that is produced in each of the following cases: [5] (i) Sulphur is oxidized by concentrated nitric acid. (ii) Action of dilute hydrochloric acid on sodium sulphide. (iii) Action of cold and dilute nitric acid on copper. (iv) At the anode during the electrolysis of acidified water. (v) Reaction of ethanol and sodium. (i) Nitrogen dioxide (ii) Hydrogen sulphide (iii) Nitrogen monoxide (iv) Oxygen (v) Hydrogen Fill up the blanks with the correct choice given in brackets. [5] (i) Ionic or electrovalent compounds do not conduct electricity in their state. (fused/solid) (ii) Electrolysis of aqueous sodium chloride solution will form at the cathode. (hydrogen gas/sodium metal) (iii) Dry hydrogen chloride gas can be collected by displacement of air.. (downward/upward) (iv) The most common ore of iron is . (calomine/haematite) (v) The salt prepared by the method of direct combination is . (iron (II) chloride/ iron (III) chloride) (i) solid (ii) hydrogen gas (iii) upward (iv) haematite (v) iron (III) chloride SECTION - II (40 MARKS) (Attempt any four questions from this Section) Question 2. (a) (i) What do you understand by a lone pair of electrons? [3] Ch- 216 2018 (ii) Draw the electron dot diagram of Hydromium ion. (H = 1, O = 8) Ans. (i) The unshared pair of electron that does not normally take part in a chemical reaction is known as lone pair. X H X X N X H lone pair of electron X bond pair H (ii) Hydronium ion Formation of proton : H(1) 1e H + H(1) H Structure of water O (8) O H X X X O X X X H H X X O X X H Formation of hydronium ion H XX O XX H + + H H X X O + H H Hydronium ion (b) In Period 3 of the Periodic Table, element B is placed to the left of element A. [3] On the basis of this information, choose the correct word from the brackets to complete the following statements: (i) The element B would have (lower/higher) metallic character than A. (ii) The element A would probably have (lesser/higher) electron affinity than B. (iii) The element A would have (greater/smaller) atomic size than B. Ans. (i) Higher (ii) Higher (iii) Smaller (c) Copy and complete the following table which refers to the conversion of ions to neutral particles. [4] Ch- 217 2018 Conversion Chloride ion to chlorine molecule Lead (II) ion to lead Ans. Conversion Chloride ion to chlorine molecule Lead (II) ion to lead Ionic Equation Oxidation/Reduction (i) (iii) (ii) (iv) Ionic Equation Oxidation/Reduction (i) Cl le Cl Cl + Cl Cl2 (iii) Pb2+ + 2e Pb (ii) Oxidation 3 (iv) Reduction Question 3. (a) (i) Write the balanced chemical equation to prepare ammonia gas in the laboratory by using an alkali. [3] (ii) State why concentrated sulphuric acid is not used for drying ammonia gas. (iii) Why is ammonia gas not collected over water? Ans. (i) 2NH4Cl Ammonium chloride + Ca(OH)2 CaCl2 + 2H2O + 2NH3 Calcium hydroxide (ii) Concentrated sulphuric acid reacts with ammonia / form ammonium sulphate or NH being basic combines with concentrated H2SO4 / correct chemical equation. 2NH3 + H2SO4 (NH4)2SO4 (iii) Ammonia is highly soluble gas one volume of water can dissolve 702 volumes of ammonia at 20 C and at 1 atmospheric pressure. Hence, it is not collected over water. (b) (i) Name the acid used for the preparation of hydrogen chloride gas in the laboratory. Why is this particular acid preferred to other acids? [3] (ii) Write the balanced chemical equation for the laboratory preparation of hydrogen chloride gas. Ans. (i) Concentrated sulphuric acid [It is preferred to other acids because it is non-volatile acid] C (ii) NaCl + H2SO4 below 200 NaHSO4 + HCl (c) For the preparation of hydrochloric acid in the laboratory: [2] (i) Why is direct absorption of hydrogen chloride gas in water not feasible? (ii) What arrangement is done to dissolve hydrogen chloride gas in water? Ans. (i) Direct absorption of hydrogen chloride gas in water is not feasible as it leads to back suction. (ii) Inverted funnel arrangement is done to dissolve hydrogen chloride gas in water. (d) For the electro-refining of copper [2] (i) What is the cathode made up of ? (ii) Write the reaction that takes place at the anode. Ch- 218 2018 Ans. (i) Cathode is made-up of thin sheets of pure copper connected in parallel. (ii) Cu 2e Cu2+ Copper anode undergoes oxidation forming Cu2+ ions which pass into the solution. Question 4. (a) The percentage composition of a gas is: [2] Nitrogen 82.35%, Hydrogen 17.64% Find the empirical formula of the gas. [N = 14, H = 1] Ans. Symbol Percentage Atomic wt. Relative Ratio Simplest Ratio Nitrogen 82.35% 14 82.35 = 5.88 14 5.88 =1 5.88 Hydrogen 17.64% 1 17.64 = 17.64 1 17.64 =3 5.88 Empirical Formula = N1H3 = NH3 (b) Aluminium carbide reacts with water according to the following equation: [4] Al4C3 + 12H2O 4Al(OH)3 + 3CH4 (i) What mass of aluminium hydroxide is formed from 12 g of aluminium carbide? (ii) What volume of methane at s.t.p. is obtained from 12 g of aluminium carbide? [Relative molecular weight of Al4Cl3 = 144; Al(OH)3 = 78] Ans. (i) Al4C3 + 12H2O 4Al(OH)3 + 3CH4 [4 27 + 3 12] 108 + 36 144 g 4[27 + 17 3] 4[27 51] 4 78 312 g 144 g of Al4Cl3 produce 312 g of Al(OH)3 1 g of Al4C3 produce 12 g of Al4C3 produce 312 g of Al(OH)3 144 312 12 = 26 g of Al(OH)3 144 (ii) Al4C3 + 12H2O 4Al(OH)3 + 3CH4 144 g 3 22.4 l 67.2 l 144 g of Al4C3 will produce 67.2 l of methane 1 g of Al4C3 will produce 12 g of Al4C3 will produce 67.2 l of methane 144 67.2 12 = 5.6 l 144 Ch- 219 2018 (c) (i) If 150 cc of gas A contains X molecules, how many molecules of gas B will be present in 75 cc of B? [2] The gases A and B all under the same conditions of temperature and pressure. (ii) Name the law on which the above problem is based. Ans. (i) 150 cc of gas A contain X molecules 150 cc of gas B will also contain X molecules 75 cc of gas B will contain X molecules under the same conditions of temperature 2 and pressure. (ii) Avogadro s law (d) Name the main component of the following alloys: [2] (i) Brass (ii) Duralumin Ans. (i) Brass Copper, zinc and tin. (ii) Duralumin Aluminium, copper, magnesium and manganese. Question 5. (a) Complete the following table which relates to the homologous series of hydrocarbons. [6] General formula IUPAC name of the homologous series Characteristic bond type IUPAC name of the first member of the series CnH2n 2 CnH2n + 2 (A) (D) (B) (E) (C) (F) Ans. (A) (C) (E) (b) (i) Alkynes (B) Triple covalent bond Ethyne (D) Alkane Single covalent bond (F) Methane Name the most common ore of the metal aluminium from which the metal is extracted. Write the chemical formula of the ore. [4] (ii) Name the process by which impure ore of aluminium gets purified by using concentrated solution of an alkali. (iii) Write the equation for the formation of aluminium at the cathode during the electrolysis of alumina. Ans. (i) Bauxite (Al2O3 2H2O) (ii) Baeyer s process (iii) Al2O3 2Al3+ + 3O2 Cation (Cathode) Cathode Al3+ + 3e Al Anion Ch- 220 2018 Question 6. (a) A compound X (having vinegar like smell) when treated with ethanol in the presence of the acid Z, gives a compound Y which has a fruity smell. [4] The reaction is: z C2H5OH + X Y + H2 O (i) Identify Y and Z. (ii) Write the structural formula of X. (iii) Name the above reaction Ans. CH3 COO H X (i) + C2H5 OH H2SO4 Z CH3 COO C2H5 + H 2O Ethyl ethanoate Y is ethyl ethanoate and Z is concentrated sulphuric acid. H O (ii) H C C OH H (iii) Esterification reaction (b) Ethane burns in oxygen to form CO2 and H2O according to the equation: 2C2H6 + 7O2 4CO2 + 6H2O If 1250 cc of oxygen is burnt with 300 cc of ethane. Calculate: (i) the volume of CO2 formed. (ii) the volume of unused O2 . Ans. 2C2H6 + 7O2 4CO2 + 6H2O 2 vol 7 vol 300 cc (i) 2C2H6 + 7O2 4CO2 + 6H2O 2 vol 4 vol 300 cc 2 vol. of ethane forms 4 volumes of carbon dioxide 1 vol. of ethane forms 300 cc will form 4 volumes of carbon dioxide. 2 4 300 = 600 cc of CO2. 2 (ii) 2 vol. of ethane requires 7 volumes of oxygen [4] Ch- 221 2018 2 vol. of ethane requires 7 volumes of oxygen 2 300 cc of ethane requires 7 300 = 1050 cc 2 Total volume of oxygen = 1250 cc Volume of oxygen used = 1050 cc Unused oxygen = (1250 1050) cc = 200 cc (c) Three solutions P, Q and R have pH value of 3.5, 5.2 and 12.2 respectively. [2] Which one of these is a : (i) Weak acid? (ii) Strong alkali? Ans. P = 3.5 Q = 5.2 R = 12.2 1 Strongly Acidic 14 7 3.5 5.2 12.2 weak acid Strong alkali Strongly Basic (i) Weak acid = Q (ii) Strong alkali = R Question 7. (a) Give a chemical test to distinguish between the following pairs of chemicals: [4] (i) Lead nitrate solutioni and Zinc nitrate solution. (ii) Sodium chloride solution and Sodium nitrate solution. Ans. (i) Add ammonium hydroxide to the solutions of lead nitrate and zinc nitrate dropwise and then in excess. Lead Nitrate 1. 2. On adding ammonium hydroxide chalky white precipitates of lead hydroxide are formed. Pb(NO3)2 + 2NH4OH Pb(OH)2 + 2NH4NO3 On adding excess of ammonium hydroxide, the precipitates do not dissolve. Zinc Nitrate 1. 2. On adding ammonium hydroxide gives colourless precipitates of zinc hydroxide are formed. Zn(NO3)2 + 2NH4OH Zn(OH)2 + 2NH4NO3 On adding excess of ammonium hydroxide, the precipitates dissolves forming a soluble complex. Zn(OH)2 + 2NH4NO3 + 2NH4OH [Zn(NH3)4] (NO3)2 + 4H2O Ch- 222 2018 (ii) Add silver nitrate solution to both sodium chloride and sodium nitrate solution and observe. Sodium Chloride 1. Add silver nitrate solution to sodium chloride Sodium Nitrate 1. NaCl + AgNO3 AgCl + NaNO3 You will observe curdy white precipitates of silver chloride. Add silver nitrate solution to sodium nitrate. No reaction will take place. NaNO3 + AgNO3 No reaction (b) Write a balanced equation for the preparation of each of the following salts: [2] (i) Copper sulphate from Copper carbonate (ii) Zinc carbonate from Zinc sulphate. Ans. (i) CuCO3 + H2SO4 CuSO4 + H2O + CO2 (ii) ZnSO4 + Na2SO3 ZnCO3 + Na2SO4 (c) (i) What is the type of salt formed when the reactants are heated at a suitable temperature for the preparation of Nitric acid? [2] (ii) State why for the preparation of Nitric acid, the complete apparatus is made up of glass. Ans. (i) Acid salt. (ii) All glass apparatus is used because nitric acid vapours are corrosive and may attack rubber, cork or metal. (d) Which property of sulphuric acid is shown by the reaction of concentrated sulphuric acid with : [2] (i) Ethanol? (ii) Carbon? Ans. (i) Dehydrating agent C2H5OH ethanol conc. H2SO4 160 -170 C C2H4 ethene (ii) Oxidising agent C + 2H2SO4 CO2 + 2H2O + 2SO2 ICSE QUESTION PAPER-2019 (SOLVED) PAPER 2 (CHEMISTRY) (Two hours) Answers to this Paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the Question Paper. The time given at the head of this paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. SECTION - I (40 MARKS) (Attempt all questions from this Section) Question 1. (a) Choose the correct answer from the options given below: (i) [5] An electrolyte which completely dissociates into ions is: A. Alcohol B. Carbonic acid C. Sucrose D. Sodium hydroxide (ii) The most electronegative element from the following elements is: A. Magnesium B. Chlorine C. Aluminium D. Sulphur (iii) The reason for using Aluminium in the alloy duralumin is: A. Aluminium is brittle. B. Aluminium gives strength. C. Aluminium brings lightness. D. Aluminium lowers melting point. (iv) The drying agent used to dry HCl gas is: A. Conc. H2SO4 C. A12O3 B. ZnO D. CaO (v) A hydrocarbon which is a greenhouse gas is: A. Acetylene B. Ethylene C. Ethane D. Methane (b) Fill in the blanks with the choices given in brackets: (i) [5] Conversion of ethanol to ethene by the action of concentrated sulphuric acid is an example of____________. (dehydration / dehydrogenation / dehydrohalogenation) Ch- 223 2019 Ch- 224 2019 (ii) When sodium chloride is heated with concentrated sulphuric acid below 200 C, one of the products formed is____________. (sodium hydrogen sulphate / sodium sulphate / chlorine) (iii) Ammonia reacts with excess chlorine to form____________. (nitrogen / nitrogen trichloride / ammonium chloride) (iv) Substitution reactions are characteristic reactions of ____________. (alkynes / alkenes / alkanes) (v) In Period 3, the most metallic element is ____________. (sodium /magnesium / aluminium) (c) Write a balanced chemical equation for each of the following reactions: (i) Reduction of copper (II) oxide by hydrogen (ii) Action of dilute sulphuric acid on sodium hydroxide [5] (iii) Action of dilute sulphuric acid on zinc sulphide (iv) Ammonium hydroxide is added to ferrous sulphate solution (v) Chlorine gas is reacted with ethene. (d) State one observation for each of the following: [5] (i) Concentrated nitric acid is reacted with sulphur. (ii) Ammonia gas is passed over heated copper (II) oxide (iii) Copper sulphate solution is electrolysed using copper electrodes (iv) A small piece of zinc is added to dilute hydrochloric acid (v) Lead nitrate is heated strongly in a test tube. (e) (i) Calculate : [5] 1. The number of moles in 12g of oxygen gas. 2. The weight of 1022 atoms of carbon. [O = 16] [C = 12, Avogadro s No. = 6 1023] (ii) Molecular formula of a compound is C6H18O3. Find its empirical formula. (f) (i) Give the IUPAC name of the following organic compounds: [5] H H O | | || 1. H C C=C H 2. H C C H | | H H (ii) What is the special feature of the structure of ethyne? (iii) Name the saturated hydrocarbon containing two carbon atoms. (iv) Give the structural formula of Acetic acid. (g) Give the appropriate term defined by the statements given below: [5] Ch- 225 2019 (i) The formula that represents the simplest ratio of the various elements present in one molecule of the compound. (ii) The substance that releases hydronium ion as the only positive ion when dissolved in water. (iii) The tendency of an atom to attract electrons towards itself when combined in a covalent compound. (iv) The process by which certain ores, specially carbonates, are converted to oxides in the absence of air. (v) The covalent bond in which the electrons are shared equally between the combining atoms. (h) Arrange the following according to the instructions given in brackets: (i) K, Pb, Ca, Zn. (In the increasing order of the reactivity) [5] (ii) Mg2+, Cu2+, Na1+, H1+ (In the order of preferential discharge at the cathode) (iii) Li, K, Na, H (In the decreasing order of their ionization potential) (iv) F, B, N, O (In the increasing order of electron affinity) (v) Ethane, methane, ethene, ethyne. (In the increasing order of the molecular weight) [H = 1, C = 12] Answer : (a) (i) D Sodium hydroxide (iii) C Aluminium brings lightness (v) D Methane (b) (i) Dehydration (iii) Nitrogen trichloride (v) Sodium (c) (i) (ii) B Chlorine (iv) A Conc. H2SO4 (ii) Sodium hydrogen sulphate (iv) Alkanes CuO + H2 Cu + H2O (ii) 2NaOH + H2SO4 (dil) Na2SO4 + 2H2O (iii) ZnS + H2SO4 (dil) ZnSO4 + H2S (iv) FeSO4 + 2NH4OH Fe(OH)2 + (NH4)2SO4 (v) C2H4 + Cl2 C2H4Cl2 (d) (i) Reddish brown gas is observed (ii) Black solid copper oxide changes into reddish brown solid (iii) At cathode : Pink or reddish brown Cu is deposited At anode : anode keep dissolving Or Size of cathode increases and size of anode decreases. Or (iv) a gas released which burns with pop sound (v) Reddish brown gas or yellow oxide i.e. PbO Ch- 226 (e) (i) 2019 1. GMM O2 = 32 gm 32 gm of O2 contains = 1 mole molecules 1 gm of O2 contains = 1 32 1 3 12 = = 0 375 32 8 23 2. 6 10 atoms of carbon has mass = 12 gm 12 gm of O2 contains = 1 atom of carbon has mass = 12 6 1023 1022 atoms of carbon has mass = 12 6 1023 1022 = 2 = 0 2gm 10 (ii) Empirical formula of C6H18O3 = C2H6O1 (f) (i) Propyne (ii) Ethanal (iv) Ethane C2H6 (iii) Triple bond H O | || (v) H C C O H | H (g) (i) Empirical formula (ii) Acid (iv) Calcination (h) (i) (iii) Electronegativity (v) Non polar covalent bond Pb < Zn < Ca < K (iii) H > Li > Na > K (ii) Na+ < Mg2+ < H+ < Cu2+ (iv) B < N < O < F (v) CH4 < C2H2 < C2H4 < C2H6 SECTION II (40 Marks) Attempt any four questions from this Section Question 2. (a) Draw the electron dot structure of: (i) Nitrogen molecule [N = 7] [3] (ii) Sodium chloride [Na = 11, Cl = 17] (iii) Ammonium ion [N = 7, H = l] (b) The pH values of three solutions A, B and C are given in the table. Answer the following questions: [3] Ch- 227 2019 Solution pH value A 12 B 2 C 7 (i) Which solution will have no effect on litmus solution? (ii) Which solution will liberate CO2 when reacted with sodium carbonate? (iii) Which solution will turn red litmus solution blue? (c) Study the extract of the Periodic Table given below and answer the questions that follow. Give the alphabet corresponding to the element in question. DO NOT repeat an element. [4] A C D B E G F (i) Which element forms electrovalent compound with G? (ii) The ion of which element will migrate towards the cathode during electrolysis? (iii) Which non-metallic element has the valency of 2? (iv) Which is an inert gas? Answer. (a) (i) Nitrogen molecules N2 N (ii) Sodium chloride NaCl N Na (iii) Ammonium ion N N Na+ Cl Cl H + H N H H (b) (i) C (ii) B (iii) A (c) (i) B Question 3. (ii) C (iii) E(iv) F (a) Name the particles present in: [3] Ch- 228 2019 (i) Strong electrolyte (ii) Non- electrolyte (iii) Weak electrolyte (b) Distinguish between the following pairs of compounds using the reagent given in the bracket. [3] (i) Manganese dioxide and copper (II) oxide, (using concentrated HCl) (ii) Ferrous sulphate solution and ferric sulphate solution, (using sodium hydroxide solution) (iii) Dilute hydrochloric acid and dilute sulphuric acid, (using lead nitrate solution) (c) Choose the method of preparation of the following salts, from the methods given in the list: [4] [List: A. Neutralization B. Precipitation C. Direct combination D. Substitution] (i) Lead chloride (ii) Iron (II) sulphate (iii) Sodium nitrate (iv) Iron (III) chloride Answer. (a) (i) Strong electrolyte only ions (ii) Non electrolyte only molecules (iii) Weak electrolyte ions as well as molecules (b) (i) MnO2 and CuO (using conc. HCl) MnO2 + Conc. 4HCl MnCl2 + 2H2O + Cl2 [greenish yellow gas chlorine is obserbved] CuO + 2HCl CuCl2 + H2O [but not coloured gas is observed] (ii) FeSO4 and Fe(SO4)3 (using NaOH sol.) FeSO4 + 2NaOH (sol.) Fe(OH)2 + Na2SO4 dirty green ppt. Fe2(SO4)3 + 6NaOH 2Fe(OH)3 + 3Na2.SO4 [Reddish brown ppt.] (iii) Dil. HCl and Dil. H2SO4 (using Pb (NO3)2) Pb(NO3)2 + 2HCl PbCl2 + 2HNO3 white ppt. of PbCl2 dissolve on heating Pb(NO3)2 + H2SO4 PbSO4 + 2HNO3 [Insoluble ppt. of PbSO4] (c) (i) Lead chloride Precipitation (ii) Iron (II) sulphate Substitution (iii) Sodium Nitrate Neutralization Question 4. (iv) Iron (III) chloride Direct combination (a) Complete the following equations: [3] Ch- 229 2019 S + conc. HNO 3 (iii) Cu + dil. HNO3 (ii) C + conc. H2SO4 (i) (b) Write a balanced chemical equation for the preparation of: (i) Ethene from bromoethane [3] (ii) Ethyne using calcium carbide (iii) Methane from sodium acetate. (c) Name the following organic compounds: (i) [4] The compound with 3 carbon atoms whose functional group is a carboxyl. (ii) The first homologue whose general formula is CnH2n. (iii) The compound that reacts with acetic acid to form ethyl ethanoate. (iv) The compound formed by complete chlorination of ethyne. Answer. (a) (i) S + Conc. 6HNO3 H2SO4 + 2H2O + 6NO2 (ii) C + Conc. 2H2SO4 CO2 + 2H2O + 2SO2 (iii) 3Cu + dil. 8HNO3 3Cu(NO3)2 + 4H2O + 2NO (b) (i) Ethene from bromoethane C2H5Br Bromothane + KOH C2H4 + KBr + H2O alcoholic ethene (ii) Ethyne using calcium carbide CaC2 + 2H2O Ca(OH)2 + C2H2 Calcium carbide ethyne (iii) Methane from sodium acetate CH3COONa + NaOH CH4 + Na2CO3 Sodium acetate Methane O || (c) (i) CH3CH2 C OH Propanoic acid (ii) C2H4 Ethene (iii) C2H5OH Ethanol Cl Cl | | (iv) 1, 1, 2, 2, tetrachloroethane H C C H | | Cl Cl Ch- 230 2019 Question 5. (a) Give the chemical formula of : (i) Bauxite [3] (ii) Cryolite (iii) Sodium aluminate (b) Answer the following questions based on the extraction of aluminium from alumina by Hall-Heroult s Process.: (i) [3] What is the function of cryolite used along with alumina as the electrolyte? (ii) Why is powdered coke sprinkled on top of the electrolyte? (iii) Name the electrode, from which aluminium is collected. (c) Match the alloys given in column I to the uses given in column II: COLUMN I [4] COLUMN II (i) Duralumin A. Electrical fuse (ii) Solder B. Surgical instruments (iii) Brass C. Aircraft body (iv) Stainless Steel D. Decorative articles Answer. (a) (i) Bauxite Al2O32H2O (ii) Cryolite Na3AlF6 (iii) Sodium aluminate Na3AlO3 (b) (i) 1. to lower the fusion temperature of alumina 2. Enhance conductivity of Alumina (ii) 1. prevent burning of anode 2. reduces the heat loss by radiation (iii) Cathode (c) Match the alloys (i) Duralumin C Aircraft body (ii) Solder A Electric fuse (iiii) Brass D Decorative material (iv) Stainless steel B Surgical instrument Question 6. (a) Identify the substances underlined: (i) [3] The catalyst used to oxidise ammonia. (ii) The organic compound which when solidified, forms an ice like mass. (iii) The dilute acid which is an oxidizing agent. (b) Copper sulphate solution reacts with sodium hydroxide solution to form a precipitate of copper hydroxide according to the equation: [3] Ch- 231 (i) 2019 2NaOH + CuSO4 Na2SO4 + Cu (OH)2 What mass of copper hydroxide is precipitated by using 200 gm of sodium hydroxide? [H = 1, O = 16, Na = 23, S = 32, Cu = 64] (ii) What is the colour of the precipitate formed? (c) Find the empirical formula and the molecular formula of an organic compound from the data given below: [4] C = 75.92%, H = 6.32% and N = 17.76%. The vapour density of the compound is 39.5. [C=12, H=l, N=14] Answer. (a) (i) Platinum (ii) Acetic acid or Ethanoic acid, (CH3COOH) (iii) Nitric acid (b) (i) 2NaOH + CuSO4 Na2SO4 + Cu(OH)2 2 40 = 80 gm 98 gm 80 gm of NaOH is used to produce ppt. Cu(OH)2 =98 gm 1 gm of NaOH is used to produce ppt. = 98 80 200 gm of NaOH is used to produce ppt. = 98 200 = 245gm. 80 (ii) the colour of ppt. is pale blue. (c) Element %age Atomic Atomic Simplest mass ratio ratio C 75.92 12 75 92 = 6 32 12 6 32 =5 1 27 H 6.32 1 6 32 = 6.32 1 6 32 =5 1 27 N 17.76 14 17 76 = 1.27 14 1 27 =1 1.27 Empirical formula = C5H5N. Empirical formula mass = 5 12 + 5 1 + 14 = 60 + 5 + 14 = 79 Vapour density = 39.5 Molecular mass = 2 39.5 = 79 Ch- 232 2019 Molecular mass 79 =1 n = Empiricalformula mass = 79 So, Empirical formula is Molecular formula C5H5N. C5 H 5 N H H H H | | | C=C C=C C N H 2, 4-Pentadienenitrile Question 7. (a) Name the gas evolved in each of the following cases: (i) [3] Alumina undergoes electrolytic reduction. (ii) Ethene undergoes hydrogenation reaction. (iii) Ammonia reacts with heated copper oxide. (b) Study the flow chart given and give balanced equations to represent the reactions A, B and C: [3] B A NH 4 Cl NH3 Mg 3 N 4 C (c) Copy and complete the following table which refers to the industrial method for the preparation of ammonia and sulphuric acid: [4] Name of the compound Name of the process Catalytic equation (with the catalyst) Ammonia (i)____________ (ii)____________ Sulphuric acid (iii)___________ (iv)___________ (b) Ethane (c) Nitrogen Answer. (a) Carbon dioxide (b) M3N2 + 6H2O 3Mg(OH)2 + 2NH3 (A) NH3 + HCl NH4Cl (B) NH4Cl + heat (C) NH3 + HCl Ch- 233 2019 (c) Ammonia (i) Haber s Process Fe (catalyst)/Mo (promoter) (ii) Na2 + 3H2 2NH3 + heat 450 C 500 C above 200 atm. Sulphuric acid (i) Contact Process (ii) S + O2 SO2 V O /Pt. V O /Pt. 2 5 2 5 Catalytic eqn. SO2 + O2 SO3 or SO2 + O2 2SO3 SO3 + H2SO4 H2S2O7 H2S2O7 + H2O 2H2SO4 400 450 C PAGES 234 TO 1409 ARE OMITTED. BUY THE COMPLETE BOOK BY OPENING THE LINK GIVEN BELOW https://www.arundeepselfhelp.info/index.php?route=product/product&product_id=378 SPECIAL DISCOUNT OF 25% FOR SCHOOLS. USE COUPON CODE : SCH025 9 789388 395168

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