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GOLDCREST HIGH, LATUR PRE-BOARD EXAMINATION GRADE: 10 SUBJECT: SCIENCE PAPER-2 (CHEMISTRY) Time: 2 Hours Max. Marks: 80 Answer to this question must be written on the paper provided separately. You will not be allowed to write answers for the first 15 minutes. This time is to be spent on reading the question paper. The time given at the head of this paper is the time allotted for the writing the answer. The paper is divided into two sections. Attempt all questions from Section A and any four questions from Section B. 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 following statements are correct only under certain conditions. Rewrite each statement including appropriate conditions underlined in your answers (i) Sodium reacts with chlorine to form sodium chloride. (ii) The electrolysis of lead bromide liberates lead and bromine. (iii) Copper crystals are dehydrated by sulphuric acid. (iv) Calcium nitrate reacts with sodium sulphate to form calcium sulphate. (v) Metals of IA group are called alkaline earth metals. [5] (b) State one relevant observation for each of the following: [5] (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 (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) Complete the following calculations. Show working for complete credit. [5] (i) Calculate the number of moles and the number of molecules in 6.2 g of lead nitrate. [Pb=207,N=14,O=16] (ii) How many grams of ammonia will contain the same number of molecules as 1.1g of carbon dioxide. [C=12,O=16,N=14,H=1] (iii) Define the terms relative molecular mass and molar volume PB-EX/CHE/2019/KSH This question paper consists of 5 printed pages and 1 blank page Page 1 (e) From the following list of substances, choose one to match the description (i) and (v) given below. Lead chloride, Silver chloride, Magnesium chloride, Disodium Hydrogen phosphate, Washing Soda crystals . (i) It is a deliquescent substance (ii) It is an acidic salt. (iii) It is an efflorescent salt. (iv) It is a metal chloride soluble in excess of Ammonium hydroxide. (v) It is a salt soluble in hot water but insoluble in cold water. . [5] (f) (i)Draw the structural formula for each of the following: (a) Propanone (b) 1 Propanal (c) Iso butane (d) Acetone [2] (ii) Name the constituents of (a) Duralumin (b) Solder (c) Bronze (g) How will you distinguish each of the following compound by a chemical test : (i) Sodium Sulphate and Sodium Sulphide (ii) Copper hydroxide and Lead hydroxide (iii) Acetylene and ethylene (iv) Ferrous sulphate and Ferric sulphate (v) Nitric acid and sulphuric acid [3] [5] (h) Give appropriate scientific reasons for the following statements: [5] (i) A neutral gas other than oxygen is formed at the anode during electrolysis of fused alumina. (ii) An aqueous solution of HCl gas conducts electricity (iii) Pure alumina is not extracted at the fusion temperature of the electrolytic mixture. (iv) Halogens have high electron affinity. (v)The reducing power of elements increases in moving down in a group while it decreases from left to right in a period. 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: (i) (ii) (iii) (iv) (v) [5] State the numbers of valence electrons in atom J Which element shown forms ions with a single negative charge? Which metallic element is more reactive than R? Which element has its electrons arranged in four shells? Q, G, R, E. Find the odd one out and explain your choice. PB-EX/CHE/2019/KSH This question paper consists of 5 printed pages and 1 blank page Page 2 (b) Hydrogen chloride gas dissolves in water to produce neutral positively charged ions. Draw the structure of this positive ions [1] (c) Give a chemical test to distinguish between the following pairs of chemicals: [3] (i) Copper nitrate and Zinc nitrate (using excess NH4OH) (ii) Sodium nitrate solutions and sodium chloride solutions. (iii) Aluminium oxide and Zinc oxide (using KOH soln.) (d) Electronegativity value of element X is 1.0, Y is 1.5 and Z is 4.0. Which two elements will combine most readily to form (i) an ionic compound (ii) a covalent compound. [1] Question-3 (a) Complete the following table related to electrolysis by writing correctly in place of (a) to (j) S.N O ELECTROPLATING OF A SPOON 1 2 USING SILVER USING NICKEL NAME OF THE ELECTROLYTE NAME OF CATHODE (a) (f) (b) (g) NAME OF ANODE REACTION ATCATHODE (c) (h) (d) (i) [3] REACTIO N AT ANODE (e) (j) (b) For the compounds listed below, explain their significance in the extraction of aluminium (i) Bauxite (ii) Cryolite (iii) Graphite (iv) Sodium hydroxide [2] (c) Write a balanced equation for the following: (i) C2H5Br + alcoholic KOH [4] (ii) CH3CH2COONa + soda lime (iii) C2H4 + Br2 (iv) C2H5OH + Na (d) Give one point difference between Froth Flotation and Gravity Separation . [1] Question-4 (a) The questions from (i) to (v) refer to the following salt solutions listed from A to F. A. Copper sulphate B. Sodium sulphate C. Potassium chloride D. Lead acetate E. Magnesium sulphate F. Zinc chloride [5] (i)Which two solutions will give white precipitate when treated with dilute hydrochloric acid followed by barium chloride? (ii) Which two solutions will give white precipitate when treated with dilute nitric acid followed by silver nitrate solution? (iii) Which solution will give white precipitate when treated with dilute sulphuric acid or dilute hydrochloric acid? (iv) Which solution will form deep blue inky colour on treating with excess of ammonia solution? (v) Which solution will give white precipitate with excess of ammonium hydroxide solution? PB-EX/CHE/2019/KSH This question paper consists of 5 printed pages and 1 blank page Page 3 (b) State how the following conversions can be carried out. (i) Ethyl chloride to ethyl alcohol (ii) Ethyl alcohol to ethene. [3] (iii) Ethyl bromide to ethane. (c) Draw different isomers having the following molecular formula: (i) C5H12 (chain) (ii) C4H8 (position and chain). [2] Question-5 (a) The preparation of calcium sulphate from calcium carbonate is a two step process as calcium sulphate cannot be prepared by adding dilute sulphuric acid. (i) What is the first step that is required to prepare calcium sulphate from calcium carbonate? (ii) Write an equation for the reaction that takes place when first step is carried out. (iii) Why is direct addition of dilute sulphuric acid to calcium carbonate an impractical method for preparing calcium sulphate. [3] (b) A compound gave a following data: C = 57.82%, O = 38.58% and the rest hydrogen. Its relative molecular mass is 166. Find its empirical formula and molecular formula. [C =12, O = 16, H = 1] (c) Write balanced chemical equations for the following reactions. (i) Potassium hydrogen carbonate and dilute sulphuric acid. (ii) Copper oxide and dilute Hydrochloric acid (iii) Sulphur and hot concentrated Nitric acid (iv) Sodium nitrate and concentrated Sulphuric acid. [3] [4] Question-6 (a) Consider the following reaction and based on the reaction answer the following: [4] (NH4)2 Cr2O7 N2 (g) + 4H2 (g) + Cr2O3 Calculate: (i) the quantity in moles of (NH4)2 Cr2O7 if 63g of (NH4)2 Cr2O7 is heated. (ii) the quantity in moles of nitrogen formed. (iii) the volume in litres or dm3of N2 evolved at S.T.P. (iv) the mass in grams of Cr2O3 formed at the same time. [H-1,Cr-52,N-14] (b) Aluminium is extracted from its chief ore, bauxite. The ore is first purified and then the metal is extracted by electrolytic reduction [4] (i) Write three balanced equation for the purification of bauxite by Hall s process. (ii) Name a chemical used for dissolving aluminium oxide (iii) Write an equation for the reaction for the reaction which takes place at anode during the extraction of aluminium by electrolytic process. (c) Give one point difference between Deliquescent and Hygroscopic Compounds. [1] (d) Name the kind of particles present in: [1] PB-EX/CHE/2019/KSH (i) Carbonic acid (ii) Sugar solution This question paper consists of 5 printed pages and 1 blank page Page 4 Question-7 (a) Write balanced chemical reaction for the following reactions: (i) Sal ammoniac reacts with slaked lime. (ii)When excess of ammonia is treated with chlorine. (iii) Nitric acid reacts with carbon. (iv) Sulphur is heated with concentrated sulphuric acid. (v) Action of concentrated sulphuric acid on carbon [5] (b) Write the IUPAC name of the following: (i) (ii) [2] (iii) (iv) (c) Give reasons for the following: [3] (i) For the preparation of hydrochloric acid, hydrogen chloride is not directly absorbed in water. (ii) Dry HCl gas does not change the colour of blue litmus. (iii) During the manufacture of Nitric acid by Ostwald s process, before the gases are allowed to enter the oxidation chamber, the gases are sufficiently cooled. PB-EX/CHE/2019/KSH This question paper consists of 5 printed pages and 1 blank page Page 5
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