2022 YIJC H2 CHEM PRELIM P4 MS

1 ©YIJC [Turn over YISHUN INNOVA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION CANDIDATE NAME SUGGESTED ANSWERS CLASS DATE H2 CHEMISTRY 9729/04 Paper 4 Practical Paper 23 August 2022 2 hours 30 minutes Candidates answer on question paper. Additional Materials: As listed in the Confidential Instructions Insert READ THESE INSTRUCTIONS FIRST This document consists of 24 printed pages. Write your name and class in the spaces at the top of this page. Give details of the practical shift and laboratory where appropriate, in the boxes provided. 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 23 and 24. 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 2 3 4 Total 55 Shift Laboratory

2 ©YIJC [Turn over Answer all the questions in the spaces provided. 1 Determination of a value for the solubility product, Ksp, of calcium iodate(V), Ca(IO3)2 The solubility in water of solid calcium iodate(V), Ca(IO3)2, is low. When a sample of this salt is mixed with water, a small amount dissolves and an equilibrium between the solid salt and its aqueous ions is established. Ca(IO3)2(s) ⇌ Ca2+(aq) + 2IO3−(aq) If separate aqueous solutions containing Ca2+ ions and IO3− ions are mixed, some of the solid salt is formed and, again an equilibrium is established. When specified volumes of potassium iodate and calcium nitrate are mixed, some calcium iodate(V) is formed as a white solid. The mixture should be left to stand for some time. After the solid is removed by filtration, the amount of iodate(V) ions left in the filtrate is determined as described below. When excess potassium iodide, KI, is added to an acidified solution containing iodate(V) ions, iodine is liberated as follows. reaction 1 IO3−(aq) + 5I−(aq) + 6H+ → 3I2(aq) + 3H2O(l) The liberated iodine is then titrated with a standard solution of sodium thiosulfate. reaction 2 2S2O32−(aq) + I2(aq) → 2I−(aq) + S4O62−(aq) In this question, you will perform a titration to determine the solubility product, Ksp, of calcium iodate(V). You are provided with: • FA 1, 0.200 mol dm−3 potassium iodate, KIO3 • FA 2, 1.00 mol dm−3 calcium nitrate, Ca(NO3)2 • FA 3, 0.0400 mol dm−3 sodium thiosulfate, Na2S2O3 • FA 4, aqueous solutio