HCI Prelim_H2_CHEM_P2

This document consists of 18 printed pages. HWA CHONG INSTITUTION C2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 15S CENTRE NUMBER INDEX NUMBER CHEMISTRY Paper 2 Structured Questions Candidates answer on the Question Paper Additional Materials: Data Booklet 9647/02 30 August 2016 2 hours INSTRUCTIONS TO CANDIDATES 1) Write your name, CT group, centre number and index number clearly in the spaces at the top of this page. 2) Answer all questions in the spaces provided in this Question Paper. INFORMATION FOR CANDIDATES The number of marks is given in brackets [ ] at the end of each question or part question. A Data Booklet is provided. Do not use staples, paper clips, highlighters, glue or correction fluid. You may use a calculator. You are reminded of the need for good English and clear presentation in your answers. For Examiner’s Use 1 / 12 2 / 17 3 / 14 4 / 13 5 / 16 Deductions Total / 72 Calculator Model:

© Hwa Chong Institution 2016 9647 / 02 / C2 Prelim 2016 2 1 Planning (P) For Examiner's use An electrochemical cell is a device that produces an electric current as a result of redox reactions. Any spontaneous redox reaction can be harnessed to produce electrical energy under the right conditions. Electrons are generated at one electrode and driv en towards the other by electromotive force, also known as the cell potential, measured in volts. The Gibbs’ Free Energy equation is given as ∆G = ∆H - T∆S. ∆G may be obtained from the cell potential of an electrochemical cell by the relationship: ∆G = -nFE where n = number of moles of electrons transferred in the reaction F = Faraday’s constant E = cell potential By constructing an electrochemical cell, the cell potential can be measured over a range of temperatures. The entropy change of a reaction can then be determined by plotting a suitable linear graph using the data obtained. (a) (i) Write an ionic equation for the reaction between Cu and Fe 3+. You should include state symbols in your equation. ………………………………………………………………………………………………[1] (ii) Predict the sign of ∆S for the above reaction. Explain your answer. ………………………………………………………………………………………………… ………………………………………………………………………………………………[1] (b) Using the information given above, you are required to write a plan for determining the entropy change for the redox reaction between Cu and Fe 3+. You will measure the cell potential over a 30 C range of temperature. You are also required to explain how the data you obtain from this experiment may be used to determine the entropy change of the reaction. You may assume that the values of ∆H and ∆S are const ant over this measured temperature change. You may also assume that you are provided with: 0.20 mol dm-3 aqueous FeCl3