DHS Prelim_H2_CHEM_P2_QP

2 This question paper consists of 16 printed pages and 2 blank pages. © DHS 2016 [Turn over Name: Index Number: Class: DUNMAN HIGH SCHOOL Preliminary Examination 2016 Year 6 H2 CHEMISTRY 9647/02 Paper 2 Structured 16 September 2016 2 hours Additional Materials: Data Booklet INSTRUCTIONS TO CANDIDATES 1 Write your name, index number and class on this cover page. 2 Answer all questions. 3 Write your answers in the spaces provided on the question paper. 4 A Data Booklet is provided. 5 The number of marks is given in brackets [ ] at the end of each question or part question. 6 You may use a calculator. Question No. 1 2 3 4 5 Total % Marks 12 15 15 15 15 [72]

2 © DHS 2016 9647/02 [Turn over Answer all questions in the spaces provided. 1 Planning (P) The reaction between peroxodisulfate ions, S 2O82, and ethanedioate ions, C 2O42, is slow and can be catalysed by Cu2+ ions. S2O82 + C2O42  2SO42– + 2CO2 To determine the rate law of this reaction, it is necessary to selectively vary the concentrations of S2O82 and C2O42 ions and determine how the rate of reaction responds to these changes. The concentrations of the reactants are varied in such a way that one is in excess compared to the other in each experiment. A suitable end point (the point at which the final time readin g is made) for the experiments will be when the reaction produced the same volume of CO 2 gas. With the measured reaction time, relative rate of the reaction can be determined. You are required to write a plan to determine the rate law of the reaction between S2O82 and C2O42 ions. (a) Suggest an explanation why this reaction is slow when performed in the absence of a catalyst. [1] (b) You may assume that you are provided with  1.00 mol dm3 peroxodisulfate ions  1.00 mol dm3 ethanedioate ions  10 cm3 aqueous copper (II) ions  the equipment and materials normally found in a school laboratory. It can be assumed that a reactant is in excess if its volume is at least five times the volume of the other reactant used. Your plan should include the following:  quantities of reactants and condition you would use in four different reaction mixtures  the measurements you would take  an outline of how one of the reaction mixtures is prepared  brief, but specific details of how the results would then be used to determine the rate law of reaction

3 © DHS 2016 9647/02 [Turn over

4 © DHS 2016 9647/02 [Turn over [8] (c) Temperature can also affect the rate of reaction and the activation energy, E a, of this reaction can be found by repeating the experiments at several different temperatures. Using equation (1) and by means of a suitable graph, the activation energy of the reaction can be determined. ln (relative rate) =  )T 1(R Ea + ln (