YIJC 2023 H2 Chem Prelim Paper 3_Tcopy (1)

©YIJC [Turn over YISHUN INNOVA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CG INDEX NO CHEMISTRY Paper 3 Free Response Candidates answer on the Question Paper. Additional Materials: Data Booklet 9729/03 14 September 2023 2 hours READ THESE INSTRUCTIONS FIRST This document consists of XX printed pages For Examiner’s Use Section A 1 / 19 2 / 22 3 / 19 Section B 4 or 5 / 20 Penalty units significant figures Overall / 80 Write your name, class and index number on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. If additional space is required, you should use the pages at the end of this booklet. The question number must be clearly shown. Section A Answer all the questions. Section B Answer one question. The use of an approved scientific calculator is expected, where appropriate. 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.

2 ©YIJC [Turn over Section A Answer all the questions in this section. 1 Alcohols are important organic compounds used in a wide variety of chemical reactions and frequently used as solvents. (a) In a fuel cell, t he direct oxidation of alcohols represents potentially the most efficient method of obtaining useful energy from a renewable fuel. For example, Direct Isopropanol Fuel Cell (DIFC) uses propan-2-ol in the fuel cell. The diagram below shows a DIFC. The Proton Exchange Membrane (PEM) allows the transfer of protons between the half-cells. The standard cell potential, Ecell o of DIFC is +1.07V. (i) By considering the given diagram , write the half -equations for the reactions occurring at electrodes A and B during discharge. Hence, write the overall equation for this reaction. [3] Electrode A: CH3CH(OH)CH3 → CH3COCH3 + 2H+ + 2e Electrode B: O2 + 4H+ + 4e → 2H2O Overall: 2CH3CH(OH)CH3 + O2 → 2 CH3COCH3 + 2H2O (ii) In certain DIFC, air containing oxygen gas could be supplied to the H 2O/O2 half- cell. Explain how the Ecell o would change, when pure oxygen, instead of air, is used for the O2/H2O half-cell. [2] With high concentration of O2, position of O 2/H2O equilibrium shifts to the right, to remove O2, resulting in a more positive E(O2/H2O) value. He