Formatting page ...
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). (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) Page 1 of 6
|
