2023 ASRJC H2 Chem Prelim P4 MS

ASRJC JC2 PRELIM 2023 9729/04/H2 ANDERSON SERANGOON JUNIOR COLLEGE 2023 JC 2 PRELIMINARY EXAMINATION NAME:________________________________ ( ) CLASS: 23 /____ CHEMISTRY 9729/04 Paper 4 Practical 24 August 2023 2 hours 30 minutes Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions READ THESE INSTRUCTIONS FIRST Write your name, class and index number on all the work you hand in. Give details of the practical shift and laboratory where appropriate, in the boxes provided. Write in dark blue or black pen. You may use a 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. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. Quantitative Analysis Notes are printed on pages 19 and 20. Shift Laboratory 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. For Examiner’s Use 1 / 14 2 / 12 3 / 16 4 / 13 Total / 55 This document consists of 19 printed pages and 1 blank page.

2 ASRJC JC2 PRELIM 2023 9729/04/H2 Answer all the questions in the spaces provided. 1 Determination of the kinetics of a redox reaction Equation 1 presents the redox reaction between iodide ions and acidified hydrog en peroxide, H2O2, to form iodine. equation 1 H 2O2(aq) + 2I–(aq) + 2H+(aq)  I2(aq) + 2H2O(l) If [H+] and [I–] are kept constant, a simplified rate equation can be obtained. rate = k’ [H2O2]n where k’ is k [H+]a [I–]b When starch is added to the reaction mixture, a blue-black colour is immedi ately seen due to the formation of an iodine-starch complex. If a small but constant amount of sodium thiosulfate , Na2S2O3, is also present in the reaction mixture, the formation of the blue-black colour is delayed. T he Na2S2O3 reacts with the I2 as shown in equation 2. equation 2 I2 + 2Na2S2O3 2NaI + Na2S4O6 FA 1 is 0.100 mol dm–3 hydrogen peroxide, H2O2. FA 2 is 0.150 mol dm–3 potassium iodide, KI. FA 3 is 1.00 mol dm–3 dilute sulfuric acid, H2SO4. FA 4 is 0.050 mol dm–3 sodium thiosulfate, Na2S2O3. Starch solution You will perform a series of four experiments and add a fixed amount of sodium thiosulfate, FA 4, to each of the experiment. You will need to ensure that the same total volume of reaction mixture is used by adding deionised water as required. The rate of this reaction is studied by measuring the time taken , t, for the blue-black colour to appear with a constant quantity of sodium thiosulfate present. Y ou will then graphically analyse your results to determine the order of reaction with r espect to hydrogen peroxide. For each experimen