23MIPrelimAS (H2 Chem Paper 4)

Class Adm No Candidate Name: This question paper consists of 18 printed pages and 0 blank page. 2023 Preliminary Examination Pre-University 3 H2 CHEMISTRY 9729/04 Paper 4 Practical 30 August 2023 2 hours 30 minutes Candidates answer on the Question paper. READ THESE INSTRUCTIONS FIRST Do not turn over this question paper until you are told to do so. Write your name, class and admission number in the spaces at the top of this page. Write in dark blue or black pen. 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. 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 17 and 18. 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. Question 1 2 3 Total Marks 18 24 13 55 Class Adm No

2 Answer all the questions in the spaces provided. 1 To determine the effect of concentration changes on the rate of a reaction FA 1, 0.0200 mol dm-3 aqueous potassium iodate(V), KIO3 FA 2, 0.0200 mol dm-3 aqueous sodium hydrogen sulfite, NaHSO3 FA 3, 0.0600 mol dm-3 aqueous sulfuric acid, H2SO4 FA 4 is starch solution In this experiment, the Landolt-Iodine clock reaction is illustrated by the following equations. IO3 - + 3HSO3 - → I- + 3SO4 2- + 3H+ equation 1 IO3 - + 5I− + 6H+ → 3I2 + 3H2O equation 2 3I2 + 3HSO3 - + 3H2O → 6I- + 3SO4 2- + 9H+ equation 3 Any I2 produced in equation 2 while HSO 3 - ions still remain in the solution is rapidly reduced to I- in equation 3. Once all the HSO 3 - ions have been used up, I2 will accumulate in the solution. When this happens, the iodine can no longer be converted back to iodide ions. The presence of iodine can be confirmed from the blue-black colour produced upon addition of starch. Overview of experiment You will carry out five similar experiments, 1 to 5 with varying concentrations of IO3 -. In each experiment, you will be required to prepare two solutions – solution A and solution B. Note:  Solution B should only be prepared once for all five experiments, while solution A must be prepared five times.  Perform the experiments in order, from experiment 1 to 5.  The measuring apparatus used to prepare solutions A and B must be kept separate at all times. For each experiment, you will record the time taken , t, for the solution to turn blue-black . The rate of the reaction is given to be, r = 𝑖𝑛𝑖