Formatting page ...
GOLDCREST HIGH-LATUR ON THE WINGS OF EXCELLENCE PRELIMINARY EXAMINATION TIME:- 2 HOURS DATE:- 22/12/2017 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. [5] (i) Among the elements given below, the element with least electronegativity: A Lithium B. Carbon C. Boron D. Fluorine (ii) The ratio between the number of molecules in 2g of hydrogen and 32g of oxygen is (H-1,O-16): A. 1:2 B. 1:0.01 C.1:1 D. 0.01:1 (iii) Which of the following would weigh the least? A. 2gram of Nitrogen B. 1 mole of silver C. 22.4 litres of oxygen gas at 1 atmospheric pressure and 273K D. 6 .02 x 1023 atoms of carbon (iv) An organic compound undergoes addition reaction and gives a red colour precipitate with ammonical cuprous chloride: A. Ethane B. Ethene C. Ethyne D. Ethanol (v) Which of the following reactions gives copper as a product: A.Passing dry ammonia over heated copper oxide B. Adding dil, HCl to Copper Oxide C. Heating Copper oxide D. Passing oxygen over heated copper oxide (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) Action of hot and concentrated Nitric acid on copper. (ii)A unsaturated hydrocarbon from calcium carbide. (iii)Reduction of hot Copper(II) oxide to copper using ammonia gas. (iv)Potassium nitrate and conc. Sulphuric acid heated below 2000C. (v)Action of sodium hydroxide on aluminium oxide. [5] (d) Give appropriate scientific reason for the following statements: [5] (i) Zinc oxide can be reduced to zinc by using carbon monoxide, but aluminium oxide can not be reduced by a reducing agent. (ii)The electrical conductivity of acetic acid is less in comparison to the electrical conductivity of dilute sulphuric acid. (iii) Dilute nitric acid is generally considered a typical acid. (iv)Why the electric bulb glows up once the concentration of the aluminium falls down in the elctrolytic chamber in the Hall s Heroult process Page 1 of 5 (v) A mixture of oxygen and ethyne is used for welding but not a mixture of ethyne and air (e) Complete the following calculations. Show working for complete credit. (i) What is the mass of nitrogen in 1000 kg urea, CO(NH2)2 ? Answer correct to nearest kg. [5] (ii) Calculate the number of moles and the number of molecules present in 1.4 g of ethylene gas. What is the volume occupied by the same amount of ethylene? What is the vapour of ethylene? (C-12,H-1). (iii)Calculate the number of molecules of water of crystallization in copper sulphate crystals, if 10 g of hydrous copper sulphate crystals gives 6.4 g of anhydrous CuSO4 on heating. (Cu-64,S-32,O-16). (f) (i)Draw the structural formula for each of the following: (a) Propanone (b) 1 Propanal (c) Iso butane (d) Acetone [2] (ii) Write balanced chemical equation for the preparation of each of the following salts: [3] (a) Ammonium Sulphate crystals (b) Lead carbonate Lead nitrate Lead Sulphate (c) Sodium Sulphate from sodium carbonate (g) Identify P.Q.R.S.T in each case based on the information given below: [5] i) A deliquescent salt P, turns yellow on dissolving in water and give a reddish brown precipitate with sodium hydroxide solution ii) The white crystalline solid Q is soluble in water. It liberates a pungent smelling gas when heated with sodium hydroxide solution. iii) The reddish brown liquid R which turns colourless when ethylene gas is passed through it. iv) A white colour soluble salt S which give gelatinous white precipitate with sodium hydroxide solution v) An amphoteric oxide T, which is used for oxidation of ammonia. (h) Given below is representation of the Modern periodic table. Answer the questions based on the data given below: [5] (i) Arrange the elements of the first group according to the increasing order of electron affinity (ii) Which element is the most metallic element? (iii) What is the similarity in electronic configuration of the halogens? (iv) Which is the most electronegative element from F and Cl and Why? (v) Which is the largest element of third period? SECTION-II (40 MARKS) (Attempt any four questions from this section) Question-2 (a) Give one test each to distinguish between the following pairs of chemicals: (i)Zinc nitrate solution and calcium nitrate solution. (ii)Sodium nitrate solutions and sodium chloride solutions. (iii)Iron(III) chloride solutions and copper chloride solutions Page 2 of 5 [3] (b) Acids dissolve in water to produce positively charged ions. Draw the structure of this positive ions [1] (c) Give balanced chemical equations for each of the following: (i) Lab preparation of ammonia using ammonium salts (ii) Reaction of excess ammonia with chlorine (iii) Reaction of ammonia with sulphuric acid [3] (d) Draw a neat and well labelled diagram for the silver plating on an iron spoon. Show relevant reactions where ever possible [2] (e) Name the kind of particles present in: (i) Carbonic acid (ii) Sugar solution [1] Question-3 (a)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 to which M belongs. (iv)State the reaction taking place at the cathode. (v) Name the product at the anode [5] (b) Complete the table NAME OF THE PROCESS ELECTROLYTE USED AND ITS DISSOCIATION REACTION [2] REACTION AT CATHODE REACTION AT ANODE PRODUCT AT CATHODE PRODUCT AT ANODE 1. HALL S HEROULT PROCESS 2. HOOPE S PROCESS (c) Name the constituents of (i) Duralumin (ii) Solder (iii) Bronze (iv)Stainless Steel (d) What are Spurious and Denatured Alcohol? [2] [1] Question-4 (a) Give balanced chemical equations for the action of sulphuric acid on each of the following: (i)Hydrated copper sulphate (ii) Sulphur Page 3 of 5 [2] (b) Complete the table:- [2] NAME OF INPUTS CATALYST TEMPERATURE PRESSURE OUTPUT PROMOTER(IF) CHEMICAL THE EQUATION PROCESS OSTWALD S PROCESS HABER S PROCESS (c) Draw different isomers having the following molecular formula: (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) Write equations for: (i) Preparation of ethanol by hydration of C2H4. (ii) Preparation of acetic acid from ethanol. (iii) Ethyne from 1, 2 dibromethane (iv) Sodium Ethoxide from sodium [4] (b) State the inference drawn from the following observations: (i) On carrying out the flame test with a salt P a red brick flame was obtained. What is the cation present in P? (ii) PH of liquid is 10.What kind of substance is Q? (iii) Salt R is prepared by reacting dilute sulphuric acid with copper. Identify R [3] (c) Define the following: (i) Deliquescent Substance (ii) Hygroscopic Substance (iii) Levigation [3] Question-6 (a) Give a chemical test to distinguish between : (i) Dilute Sulphuric acid and dilute hydrochloric acid ii) Dilute sulphuric acid and concentrated sulphuric acid [2] (b) Arrange the following as per the guidelines in the brackets: (i) Mg, Cl, Na, S, Si (decreasing order of atomic size) (ii) Cl, F, Br, I (decreasing order of electron affinity) (iii) OH-1, SO4-2, Cl-1 (in increasing ease of discharge) [3] Page 4 of 5 (c) The diagram given below shows the preparation of nitric acid in the laboratory. Observe the diagram and answer the questions given below: (i) Identify A, B and C .Write a balanced reaction for the preparation of nitric acid. (ii) Why is concentrated sulphuric acid preferred over hydrochloric acid? (iii) How is nitric acid collected? (iv) What is the special feature of the apparatus? (v) What would happen if the temperature is increased above 2000 C [5] Question-7 (a) 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 (b) P + 5 HNO3 (conc) H3PO4 + H2O + 5 NO2. If 9.3 g of phosphorus was used in the reaction. Calculate (i) the number of moles of phosphorus taken (ii) the mass of phosphoric acid formed (iii) the volume of NO2 produced at stp. (H-1,N-14,P-31,O-16) [3] (c) Write the IUPAC name of the following: (i) [2] (ii) (d) Identify the following cations: Sodium hydroxide solution is added to solution A. A white ppt is formed which is insoluble in excess sodium hydroxide solution. When ammonium hydroxide is added to solution B, a pale blue precipitate appears, this pale blue ppt disappears with excess of NH4OH is added to for form a inky blue solution. Solution C produces a dirty green ppt on addition of sodium hydroxide whereas solution D produces a yellowish brown ppt. [2] ___________________________________ END______________________________________________ Page 5 of 5
|
