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GOLDCREST HIGH-LATUR ON THE WINGS OF EXCELLENCE PRE-BOARD EXAMINATION TIME: 2 HOURS DATE:-25/1/2018 GRADE: 10 MARKS: 80 SCIENCE PAPER-02 (CHEMISTRY) General Instructions 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 the paper is the time allotted 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) Choose the most appropriate answer. (i) Which of the following forms an acidic solution in water: A CuSO4 B. Na2SO4 [5] C. Na2CO3 D. NaCl (ii) A gas cylinder of capacity of 20 dm3 is filled with gas X the mass of which is 10g.When the same cylinder is filled with hydrogen gas at the same temperature and pressure the mass of hydrogen is 2g, hence relative molecular mass of the gas is : A. 5 B. 10 C. 15 D. 20 (iii) PH of human blood is: A: 6.4 B: 7.4 C:7.2 D:9.4 (iv) The formation of 1,2 dibromoethane from ethane and bromine is an example of: A. Substitution B. Dehydration C. Dehydrohalogenation D. Halogenation (v) An oxide which is white when cold and yellow when hot and dissolves on heating with excess of caustic soda is: A. MgO B. PbO C: Fe2O3 D: ZnO (b) State one relevant observation for each of the following: (i)When the gaseous product obtained by dehydration of ethyl alcohol is passed through bromine water. (ii)When hydrogen sulphide gas is passed through lead acetate solution. (iii)At the anode when aqueous copper sulphate solution is electrolyzed with copper electrodes (iv)Excess of chlorine gas is reacted with ammonia gas. (v)Water is added to the product formed when aluminium is burnt in a jar of nitrogen gas [5] (c) Write balanced chemical equations for each of the following: (i) Red lead is warmed with concentrated hydrochloric acid. (ii) Copper sulphate to tetramine copper sulphate (iii) Ethylene from alkyl halide (iv) A mixture of carbon and concentrated nitric acid is heated. (v) Acetic acid with sodium hydroxide solution [5] (d) Complete the following calculations. Show working for complete credit. [5] (i) If a crop of wheat removes 40kg of nitrogen per hectare of soil, what mass of the fertilizer urea CO(NH2)2 ,would be required to replace the nitrogen of a 5 hectare field? (C-12,H-1,O-16,N-14). PRE-BOARD EXAM/17-18/KHM This paper consists of 6 printed pages Page 1 (ii) A cylinder can hold 1.4kg of hydrogen at STP. Calculate (a) The weight of nitrogen and of chlorine it can hold at STP. (b) The number of molecules of each of the above gases present in the flask. (N-14,Cl-35.5) (iii) 88g of a compound of carbon and oxygen only, contains 64g of oxygen. Determine its empirical formula.(C-12,O-16) (e) Give appropriate scientific reason for the following: (i)Aqueous solution of ammonia is used to remove grease stains from woolen cloths (ii)Aluminium is highly reactive metal still used for making utensils. (iii) The ratio of hydrogen and oxygen formed at the cathode and anode is 2:1 by volume on electrolysis of water (iv)Alkenes are known as Olefins. (v) Fused calcium chloride is used in the preparation of ferric chloride salt. [5] (f) (i)Draw the structural formula for each of the following: [2] (a) The third member of carboxylic acid a branched chain (b) Formaldehyde (c)Formic acid (d) An isomer of C4H10 which has (ii) Some methods used for the laboratory preparation of Salts are A: Metal + acid B: Carbonate + acid C: Precipitation D: Direct combination Copy and complete the following table: Salt 1.Ammonium sulphate 2.Calcium carbonate 3.Iron (III) chloride 4.Lead nitrate 5.Zinc sulphate 6.Iron Sulphide [3] E: Titration Method of Preparation (g) Identify P.Q.R.S.T in each case based on the information given below: [5] (i) The white crystalline solid P is soluble in water. It liberates a pungent smelling gas when heated with caustic soda solution. (ii) An element Q which reacts with concentrated Nitric Acid to form sulphuric acid. (iii) A white crystalline salt R is warmed with calcium hydroxide solution. A gas is given off which turns moist red litmus paper blue. (iv) The nitrate S does not leave any residue on heating. (v) A white solid T gives a non-persistent brick red flame. On heating with dilute sulphuric acid, it gives off a colourless and suffocating smell gas which turns acidified potassium dichromate solution green. (h) Elements A,B,C,D,E and F have the following atomic numbers: A-12. B-17, C-18, D-7, E-9, F-11. Answer the following with respect to the information provided above. [5] (i) Which one of them has the lowest electron affinity? (ii) Which one of them has the highest electron affinity? (iii) Which one of them has the largest atomic size.? (iv) Which one of them belongs to third period and has the highest ionisation potential.? (v) Draw an electron dot diagram to show the compound between A and B. PRE-BOARD EXAM/17-18/KHM This paper consists of 6 printed pages Page 2 SECTION-II (40 MARKS) (Attempt any four questions from this section) Question-2 (a) Give a chemical test to distinguish between the following pairs of chemicals: (i)Ammonium chloride and potassium chloride (iii) Calcium nitrate and zinc nitrate [3] (ii)Sodium chloride and sodium sulphide (b) Ammonia dissolves in water to produce neutral positively charged ions. Draw the structure of this positive ions [1] (c) Give balanced chemical equations for the preparation of the following: [5] (i) Chloroform from methane (ii) Ethyl acetate from ethanol (iii) Ethanol from ethene (iv)Ethyne from ethylene dibromide (v)Ethane from ethyl bromide (d) Name the substance added to each substance given below to obtain the product given in the bracket. (i) Bauxite (to obtain sodium aluminate) (ii) Aluminium (to obtain sulphur dioxide) [1] Question-3 (a) With reference to the first three periods of the modern periodic table, answer the questions given below: [4] (i) How many electrons are present in the valence shell of the element with atomic number 18? (ii) State the position of Silicon in the modern periodic table. (iii) Name the element that has highest ionization potential in the second period. (iv)Arrange the elements of first group in the increasing order of metallic character. (b) Give the balanced equations for the following conversions: [2] (c) State the property of alloys given below which make it useful for the particular application (i) Solder in electric fuse (ii) Duralumin in air crafts (iii) Stainless steel in cutlery (iv) Bronze in statues [2] (d) Define the periodic property, Electron affinity and Electronegativity [1] (e) What are amphoteric oxides? Give a reactions to support your answer [1] Question-4 (a) Give balanced chemical equations for the action of nitric acid on each of the following: PRE-BOARD EXAM/17-18/KHM This paper consists of 6 printed pages [3] Page 3 (i)Powdered sulphur (ii) Copper turnings (iii) Phosphorus (b) Complete the table:- [1] NAME OF THE PROCESS INPUTS CATALYST EQUATION FOR CATALYTIC REACTION Ammonia + air (c) Draw different isomers having the following molecular formula: OUTPUT Nitric acid (i) C5H12 (chain) (ii) C4H8 (position and chain). [2] (d) A gaseous compound of nitrogen and hydrogen contains 12.5 % hydrogen by mass. Find the molecular formula of the compound if its relative molecular mass is 37.(N-14,H-1). [2] (e) Name the organic compound prepared by each of the following reactions: (i) C2H5Br + KOH (alc) [2] (ii) C2H5Br + KOH (aq) Question-5 (a) Calcium carbide was added to a conical flask and was treated with water. A gas (G) evolved out. (i) Name the gas (G) (ii) Draw its graphic structure (iii) Write balanced chemical equation for its complete combustion in oxygen. (iv) Mention one economic importance of gas (G). [4] (b) State the inference drawn from the following observations: [3] (i) Dilute hydrochloric acid is added to sodium thiosulphate. (ii) A piece of iron is added to copper [II] sulphate solution. (iii) A paper dipped in potassium permanganate solution is put on the mouth of a test tube containing Sulphur dioxide gas. (iv) On mixing a solution of calcium chloride with a solution of sodium carbonate. (v). Excess of ammonium hydroxide is added to a substance obtained by adding hydrochloric acid in silver nitrate solution (vi) Concentrated hydrochloric acid is added to lead (IV) oxide with warming (c) (i)Calculate the percentage of sodium in sodium aluminium fluoride (Na3 AlF6) correct to the nearest whole number. (F -19, Na - 23, Al - 27) (ii) 560 ml of carbon monoxide is mixed with 500 ml of oxygen and ignited. The chemical equation for the reaction is as follows: 2CO + O2 2CO2 Calculate the volume of oxygen used and carbon dioxide formed in the above Question-6 [3] [3] (a) PRE-BOARD EXAM/17-18/KHM This paper consists of 6 printed pages Page 4 (b) Copy and complete the following table related to electrolysis. S.NO NAME OF THE ELECTROLYTE NAME OF CATHODE NAME OF ANODE 1 H2O (acidified) Platinum foil Platinum foil 2 CuSO4 (aq) Copper Carbon 3. Sodium silver cyanide (aq) Spoon Silver block [3] REACTION AT CATHODE REACTION AT ANODE (c) 2 Pb (NO3)2 2PbO +4NO2+O2. You are provided with 3.3g lead nitrate, calculate [2] (i) Number of moles present in it (ii) Number of molecules in it. (iii) Weight of nitrogen it contains (iv) Volume of oxygen it may provide on decomposition at S.T.P (N-14,O-16,Pb-207) (d) (i) On warm weather, concentrated nitric acid turns yellow. Why is it so? How can you render this acid colourless? (ii) Dark rings are formed on wooden shelves where bottles of conc. sulphuric acid are kept [2] Question-7 (a) The diagram gives the arrangement of the apparatus used for the preparation alkaline gas. [4] (i) Identify X and Y. 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 the gas is collected? (iv)Explain why it is not collected over water (v)In the laboratory preparation of ammonia from ammonium chloride, the mouth of the flask in which the reaction is carried is kept slanting downwards. Why. (vi)The apparatus used for lab.preparation of ammonia gas should be dry. Why? (vii)Ammonia gas is not dried using drying agents like conc.H2SO4,P2O5,and fused calcium chloride.Why PRE-BOARD EXAM/17-18/KHM This paper consists of 6 printed pages Page 5 (b) The reaction between calcium carbonate and hydrochloric acid is as follows: [2] CaCO3 + 2HCl CaCl2 + H2O + CO2 (i) Calculate the number of moles of hydrochloric acid that reacts with 10g of calcium carbonate (ii) If the calcium carbonate used had 20% of calcium chloride as impurity, what would be the volume of carbon dioxide liberated? (iii) How many molecules of water are formed? [Avogadro s No = 6 x 1023 At wt. Ca = 40 C = 12, H =1 Cl = 35.5 O =16] (c) Write the IUPAC name of the following: (i) [2] (ii) (d) X is a reddish brown element. When heated with dilute nitric acid, it gives out a colourless gas Y which turns into a reddish-brown gas on coming contact with air. A blue solution of a substance Z is also formed. The crystals of substance Z when heated give out the reddish brown gas along with another gas. A black residue M is left behind. (i) Name the substance X (ii) Write an equation for the reaction of substance X with dilute nitric acid and name the gas Y. (iii) Name the substance Z and M. Write an equation for the action of heat on substance Z PRE-BOARD EXAM/17-18/KHM This paper consists of 6 printed pages [2] Page 6
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