VJC 2022 H2 Chem Prelim P4_ans and preparation list_

This document consists of 14 printed pages. © VJC 2022 9729/04/PRELIM/22 [Turn over CANDIDATE NAME CT GROUP VICTORIA JUNIOR COLLEGE PRELIMINARY EXAMINATION Higher 2 ……………………………………………….………….. …………………………….. CHEMISTRY 9729/04 Paper 4 Practical Candidates answer on the Question Paper. 29 Aug 2022 2 hours 30 minutes Additional Materials: As listed in the instructions below READ THESE INSTRUCTIONS FIRST Write your name and CT group 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. Qualitative Analysis Notes are printed on pages 13 and 14. 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. Shift Laboratory For Examiner’s Use 1 / 9 2 / 12 3 / 11 4 / 15 5 / 8 Total / 55

2 © VJC 2022 9729/04/PRELIM/22 Answer all the questions in the spaces provided. 1 In acidic solutions, iron(III) ions are reduced by iodide ions to form iron(II) ions. The iodide ions are oxidised to iodine. 2Fe3+(aq) + 2I– (aq) → 2Fe2+(aq) + I2(aq) The rate of this reaction can be investigated by using starch indicator, which turns blue-black in the presence of iodine. Sodium thiosulfate is added to the reaction mixture to react with iodine as it is formed. The blue-black colour is seen when all the thiosulfate has reacted. I2(aq) + 2S2O32–(aq) → 2I–(aq) + S4O62–(aq) You will investigate how the rate of reaction is affected by changing the concentration of the iodide ions. FA 1 is 0.050 mol dm‒3 potassium iodide, KI. FA 2 is 0.050 mol dm‒3 acidified iron(III) chloride, FeCl3. FA 3 is 0.0050 mol dm‒3 sodium thiosulfate, Na2S2O3. FA 4 is starch indicator. (a) Experiment 1 1. Use the burette labelled FA 1 to transfer 10.00 cm3 of FA 1 into a 250 cm3 conical flask. 2. Use a 25 cm3 measuring cylinder to transfer 10.0 cm3 of deionised water into the conical flask. 3. Use the burette labelled FA 3 to transfer 20.00 cm 3 of FA 3 and a 50 cm3 measuring cylinder to transfer 10 cm3 of FA 4 to the same conical flask. 4. Use a 10 cm3 measuring cylinder to measure 10 cm3 of FA 2. 5. Add this FA 2 into the same conical flask and start timing immediately. 6. Swirl the mixture once and place the conical flas