2023 JPJC J2 H2 Prelim Paper 4 Qn Paper with Mark Scheme

 Jurong Pioneer Junior College [Turn Over NAME Mark Scheme CLASS 22S JURONG PIONEER JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION 2023 CHEMISTRY 9729/04 Higher 2 Paper 4 Practical 15 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 exam 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, 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. Qualitative Analysis Notes are printed on pages 18 and 19. Shift At the end of the examination, fasten all your work securely together. Laboratory The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 2 3 4 Total This document consists of 19 printed pages.

2  Jurong Pioneer Junior College 9729/04/J2 PRELIMINARY EXAM/2023 Answer all the questions in the spaces provided. 1 Determination of the kinetics of the reaction between iodide ions and peroxodisulfate ions FA 1 is 0.0200 mol dm–3 potassium peroxodisulfate, K2S2O8. FA 2 is 1.00 mol dm–3 potassium iodide, KI. FA 3 is 0.00500 mol dm–3 sodium thiosulfate, Na2S2O3. starch indicator. Equation 1 represents the reaction between peroxodisulfate ions, S 2O8 2, and iodide ions, I–. equation 1 S2O8 2(aq) + 2I–(aq)  2SO4 2(aq) + I2(aq) When starch is added to the reaction mixture, a blue-black colour is immediately seen due to the formation of an iodine-starch complex. If a small amount of sodium thiosulfate, Na2S2O3, is also present in the reaction mixture, the formation of the blue-black colour is delayed. The Na2S2O3 reacts with I2 as shown in equation 2. equation 2 I2(aq) + 2S2O3 2–(aq) → 2I–(aq) + S4O6 2–(aq) You will perform a series of five experiments. Then you will graphical ly analyse your results in order to determine the order with respect to the concentration of the peroxodisulfate ions, [S2O8 2]. For each experiment, you will note the volume of FA 1 added, VFA1, and the time taken, t, for the reaction mixture to turn blue-black. In each experiment, you will add a fixed amount of sodium thiosulfate, FA 3, to each of your experiments. You will need to ensure that the same total volume of reaction mixture is used by adding deionised water as required. You will then calculate values for  1/t,  lg( 1/t),  lg( VFA1) For Examin