HCI 2026 H2 Chemistry Prelim P4 QP

This document has 18 pages. Any blank pages are indicated. HWA CHONG INSTITUTION C2 Preliminary Examination Higher 2 CANDIDATE NAME CT GROUP 2 5 S CENTRE NUMBER S INDEX NUMBER CHEMISTRY Paper 4 Practical 9476/04 25 August 2026 2 hours 30 minutes Candidates answer on the Question Paper. READ THESE INSTRUCTIONS FIRST • Answer all questions. • Use a black or dark blue pen. You may use a HB pencil for any diagrams or graphs. • Write your name, CT group, centre number and index number on all the work you hand in. • Write your answer to each question in the space provided. • Do not use an erasable pen. Do not use correction fluid or tape. • Do not write on any bar codes. • You may use an approved calculator. • Qualitative analysis notes are printed in the question paper • Write the details of the shift and laboratory in the boxes provided. INFORMATION • The total mark for this paper is 50. • The number of marks for each question or part question is shown in brackets [ ]. Shift Laboratory For Examiner’s Use 1 2 3 4 Total

2 © Hwa Chong Institution 2026 9476/04/C2 Preliminary Examination DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN [Turn Over Answer all questions in the spaces provided. 1 Qualitative Analysis of FA 1 Qualitative Analysis FA 1 is an aqueous solution containing two cations and one anion. In addition to having access to the usual bench reagents, you are also provided with the following: aqueous sodium thiosulfate aqueous hydrogen peroxide Carry out the tests described in Tables 1.1 and 1.2. Carefully record your observations at each stage of the tests in the tables. Test and identify any gases produced. (a) Cation test Table 1.1 test observations 1 To 2 cm depth of FA 1 in a test-tube, add aqueous sodium hydroxide dropwise, until there is no further change. Filter the mixture into a clean boiling tube. Retain both residue and filtrate for tests 2 and 3. While waiting, proceed to 1(c). 2 Warm the filtrate from test 1. Let the filtrate cool down, then add dilute sulfuric acid until there is no further change. 3 Place the filter funnel with the residue from test 1 over a clean test- tube. Carefully add dilute hydrochloric acid, a few drops at a time to dissolve the residue completely. Ensure that you have added enough dilute hydrochloric acid such that the test-tube is half filled. Stir the solution with a glass rod. Retain the resultant solution for tests 4 and 5.

3 © Hwa Chong Institution 2026 9476/04/C2 Preliminary Examination DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN [Turn Over 4 To 1 cm depth of the solution from test 3, in a test-tube, add aqueous potassium iodide dropwise, until there is no further change. Then add aqueous sodium thiosulfate until there is no further change. (ignore any ppt that might form after standing) 5 To 1 cm depth of the solution from test 3, in a test-tube, add 1 cm depth of aqueous sodium thiosulfate. Shake and observe until there is no further change. Then add aqueous sodium hydroxide until there is no further change. Then add 2 cm depth of aqueous hydrogen peroxide. [8] (b) (i) Identify the two cations in FA 1. cation 1: ………………………… cation 2: ………………………… [2]

4 © Hwa Chong Institution 2026 9476/04/C2 Preliminary Examination DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN [Turn Over (ii) Suggest and explain the roles of the following reagents. Support your answer with appropriate observations. role of aqueous potassium iodide in test 4: ………………………… explanation: ……………………………………………………………………………………….. ..……………………………………………………………………………………………………… role of aqueous hydrogen peroxide in test 5: ………………………… explanation: ……………………………………………………………………………………….. ..……………………………………………………………………………………………………… [2] (c) Anion test Table 1.2 test Observations 1 To 1 cm depth of FA 1 in a test-tube, add 1 cm depth of aqueous silver nitrate. Allow any precipitate formed to settle. Decant the solution. Wash the precipitate with deionised water and discard the washings. Add aqueous ammonia to the precipitate. [2] (d) Use your observations in (c) to identify the anion in FA 1. anion: ………………………… [1] [Total: 15]

5 © Hwa Chong Institution 2026 9476/04/C2 Preliminary Examination DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN [Turn Over 2 To determine the concentration of potassium iodate(V) You are provided with the following. FA 2 is a solution containing potassium iodate(V), KIO3. FA 3 is 1.00 mol dm−3 sulfuric acid, H2SO4. FA 4 is 0.50 mol dm−3 potassium iodide, KI. FA 5 is approximately 0.1 mol dm−3 sodium thiosulfate, Na2S2O3. Starch indicator You are to determine the concentration of potassium iodate(V) present in FA 2. In acidic conditions, potassium iodate(V) oxidises iodide ions to iodine. Titration of this iodine with a standard solution of sodium thiosulfate allows the concentration of potassium iodate(V) to be determined. IO3− + 5I− + 6H+ → 3I2 + 3H2O reaction 1 I2 + 2S2O32− → 2I− + S4O62− reaction 2 FA 2 is too concentrated for use directly. You will therefore prepare a diluted solution of FA 2. You will then use FA 5 to determine the concentration of potassium iodate(V) in the diluted solution by titration, and hence determine the concentration of potassium iodate(V) in FA 2. (a) Dilution of FA 2 1. Using a burette, measure between 49.00 cm3 and 49.50 cm3 of FA 2 into a 250 cm3 volumetric flask. Record your burette readings and the volume of FA 2 used in Table 2.1. Table 2.1 Final burette reading /cm3 Initial burette reading / cm3 Volume of FA 2 used /cm3 2. Make up the contents of the flask to the 250 cm3 mark with deionised water. Place the stopper in the flask and mix the contents thoroughly. This solution is FA 6.

6 © Hwa Chong Institution 2026 9476/04/C2 Preliminary Examination DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN [Turn Over (b) (i) Titration of FA 6 with FA 5 1. Fill a clean burette with FA 5. 2. Pipette 25.0 cm3 of FA 6 into a conical flask. 3. Use appropriate measuring cylinders to add to this flask • 20 cm3 of FA 3, • 10 cm3 of FA 4. 4. Run FA 5 from the burette into the flask until the solution becomes pale yellow. 5. Add about 10 drops of starch indicator to this flask and continue adding FA 5 until the blue-black colour just disappears. 6. Record your titration results in Table 2.2. Make certain that your recorded results show the precision of your working. 7. Repeat steps 2-6 until consistent results are obtained. Results Table 2.2 Final burette reading /cm3 Initial burette reading / cm3 Volume of FA 5 used /cm3 [4] (ii) From your titrations results, obtain a suitable volume of FA 5 to be used in your calculations. Show clearly how you obtained this volume. volume of FA 5 = ……………………………… [1]

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