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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
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