TJC_H2_CHEM_P2 Prelim

1 9647/02/TJC Prelim 2011 [Turn Over CANDIDATE NAME CIVICS GROUP / CENTER NUMBER S INDEX NUMBER CHEMISTRY 9647/02 Paper 2 Structured Questions 14th September 2011 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your Civics Group and name on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions. A Data Booklet is provided. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 23 printed pages including 1 blank page. For Examiner’s Use 1 /12 2 /18 3 /10 4 /16 5 /16 Total PRELIMINARY EXAMINATIONS HIGHER 2

2 9647/02/TJC Prelim 2011 [Turn Over 1 The literature value of standard enthalpy change of reaction between solid copper and aqueous hydrochloric acid is +64.8 kJ mol-1. Cu(s) + HCl(aq)  CuCl2(aq) + H2(g) HO reaction = +64.8 kJ mol-1 HO reaction = +64.8 kJ mol -1 is a hypothetical value as copper does not react with hydrochloric acid under normal room conditions. Hence, to determine the hypothetical value for the enthalpy change, a suitable Hess cycle needs to be constructed. To construct a suitable Hess cycle, the enthalpy change of the following two reactions needs to be determined experimentally. Reaction 1: Mg(s) + 2HC l(aq)  MgCl2(aq) + H2(g) HO 1 = x kJ mol -1 Reaction 2: Mg(s) + CuC l2(aq)  Cu(s) + MgCl2(aq) HO 2 = y kJ mol-1 (a) Draw an enthalpy cycle diagram that shows the relationship between HO reaction, HO 1 andHO 2. Hence, show how HO reaction can be calculated. [2] For Examiner’s Use

3 9647/02/TJC Prelim 2011 [Turn Over (b) An online website reported that the enthalpy change of Reaction 1 , HO 1, is about -460 kJ mol-1. Write a plan to verify if the enthalpy change of Reaction 1 , HO 1, is -460 kJ mol-1. Reaction 1: Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g) HO 1 = x kJ mol-1 You may use the apparatus normally found in the school laboratory and the following apparatus and chemical reagents.  200 cm 3 Styrofoam cu