ACJC 2026 H2 Prelim Paper 4 QP

This paper consists of 17 printed pages and 1 blank page. Anglo-Chinese Junior College JC2 Preliminary Examination Higher 2 CANDIDATE NAME FORM CLASS TUTORIAL CLASS INDEX NUMBER CHEMISTRY Paper 4 Practical You must answer on the question paper. 9476/04 3 August 2026 2 hour 30 minutes You will need: The materials and apparatus listed in the confidential instructions INSTRUCTIONS • Answer all questions. • Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs. • Write your name, centre number and index number in the boxes at the top of the page. • 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 [ ]. For Examiner’s Use Question No. Marks 1 (13 m) 2 (17 m) 3 (12 m) 4 (8 m) Presentation of answers Total (50 m) Shift Laboratory

2 ACJC2026 9476/Preliminary Examinations/2026 [Turn over Answer all the questions in the spaces provided. 1 Identification of two cations and one anion (a) FA 1 and FA 2 contain a different cation and the same anion. The volumes given in Table 1.1 are approximate and should be estimated rather than measured. Test any gas evolved during the tests. If there is no observable change, write no observable change. (i) Carry out the tests described in Table 1.1. Carefully record your observations in Table 1.1. Table 1.1 test observations with FA 1 observations with FA 2 1 Add 1 cm depth of the FA solution into a clean test- tube. Test the FA solution using Universal Indicator paper. 2 Add 1 cm depth of the FA solution into a clean boiling tube. Add 1 cm depth of aqueous sodium hydroxide slowly, with shaking, until the aqueous sodium hydroxide is in excess. Gently warm the boiling tube. 3 Add 1 cm depth of the FA solution into a clean test- tube. Add 1 cm depth of aqueous ammonia slowly, with shaking, until the

3 ACJC2026 9476/Preliminary Examinations/2026 [Turn over aqueous ammonia is in excess. 4 Add 1 cm depth of the FA solution into a clean test- tube. Add a few drops of aqueous silver nitrate, then add aqueous ammonia to the mixture, with shaking, until the aqueous ammonia is in excess. [7] (b) (i) Complete Table 1.2 to identify the cations and anion in FA 1 and FA 2. Table 1.2 FA 1 FA 2 cation present anion present [3] (ii) Explain which test was used to identify the anion. Test ………… of FA …….. was used to identify the anion. Evidence: ……………………………………………………………………………………….. ………………………………………………………………………………………………... [1] (iii) Write an equation and explain the observation of FA 2 in test 1. ……………………………………………………………………………………………………. ……………………………………………………………………………………………………. ………………………………………………………………………………………………... [2] [Total: 13]

4 ACJC2026 9476/Preliminary Examinations/2026 [Turn over BLANK PAGE

5 ACJC2026 9476/Preliminary Examinations/2026 [Turn over 2 Determination of the kinetics of a clock reaction FA 3 is 0.100 mol dm−3 potassium iodate(V), KIO3. FA 4 is 0.0500 mol dm−3 sodium hydrogensulfite, NaHSO3. You are also provided with: • starch solution • deionised water. Iodate(V) ions react with hydrogensulfite ions in aqueous solution according to the equation shown. 2IO3−(aq) + 5HSO3−(aq) I2(aq) + 5SO42−(aq) + 3H+(aq) + H2O(l) In this experiment, the rate of reaction is studied by measuring the time taken to form a fixed amount of iodine using a ‘clock’ method. In the presence of starch, a blue-black colour indicates the formation of iodine. The reaction proceeds through several steps, so the blue-black colour does not appear immediately. You will vary the concentration of iodate( V) ions and measure the time, t, taken for the blue-black complex to appear. You will perform a series of five experiments, in which the volume of FA 3 is varied while the volume of FA 4 is kept constant. In each experiment, you will adjust the volume of deionised water so that the total volume of the reaction mixture is 20.0 cm3.

6 ACJC2026 9476/Preliminary Examinations/2026 [Turn over Experiment 1 1. Use a teat pipette to add 10 drops of starch solution to a clean 100 cm3 conical flask. 2. Use a 10 cm3 measuring cylinder to measure 2.0 cm3 of FA 3 into the conical flask. 3. Use a 25 cm 3 measuring cylinder to add 16.0 cm 3 of deionised water into the same conical flask. Swirl gently to mix. 4. Use a second 10 cm3 measuring cylinder to measure 2.0 cm3 of FA 4. 5. Pour FA 4 into the conical flask, starting the stopwatch during this addition. 6. Swirl the mixture thoroughly. Place the flask on a white tile. 7. Stop the stopwatch at the first appearance of a blue-black colour. 8. Record the time taken, t, to the nearest second, in your table. 9. Wash the conical flask thoroughly with tap water, then with deionised water. Stand it upside down on a paper towel to drain. Record all volumes, the time taken and the calculated values of 1/t , log(1/t) and log(VFA3) in the space provided on page 6. Experiments 2 to 5 Repeat experiment 1 four times, using 4.0 cm 3, 6.0 cm3, 8.0 cm3 and 10.0 cm3 of FA 3 respectively in step 2. In each experiment, you should adjust the volume of deionised water in step 3 to ensure that the total volume of reaction mixture is 20.0 cm3. You should alternate the use of two 100 cm3 conical flasks. (a) Results [5]

7 ACJC2026 9476/Preliminary Examinations/2026 [Turn over (b) Plot a graph of log(1/t) on the y-axis against log(VFA3) on the x-axis for experiments 1 to 5 on the grid in Fig. 2.1. Draw the best-fit straight line. Fig. 2.1 [3]

8 ACJC2026 9476/Preliminary Examinations/2026 [Turn over (c) Calculate the gradient of your best-fit line to three significant figures, showing clearly how you did this. gradient = …………..…………………………[1] (d) The gradient of the line in (b) gives the order of reaction, n, with respect to [ IO3−]. State the value of n. n = …………………………………….. [1] (e) Explain why log(VFA3) may be plotted directly on the x-axis instead of log[IO3−] to determine the order of reaction with respect to [IO3−]. ……………………………………………………………………………………………………………. ……………………………………………………………………………………………………………. ……………………………………………………………………………………………….............. [2] (f) Planning It is suggested that an ion of transition element X serves as a catalyst in the reaction between iodate(V) and hydrogensulfite ions. (i) Suggest why the reaction between iodate(V) and hydrogensulfite ions is slow and the rate of reaction increases in the presence of a catalyst. …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… ………………………………………………………………………………………………… [2]

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