YIJC 2026 H2 Chem Prelim Paper 4 QP

1 ©YIJC 9476/04/JC2/PE/2026 [Turn over YISHUN INNOVA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CG INDEX NO CHEMISTRY Paper 4 Practical You must answer on the question paper. You will need: The materials and apparatus listed in the confidential instructions. 9476/04 13 August 2026 2 hours 30 minutes 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, class 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. • 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 [ ]. This document has 24 pages. Any blank pages are indicated. Shift Laboratory For Examiner’s Use 1 / 16 2 / 25 3 / 9 Total / 50

2 ©YIJC 9476/04/JC2/PE/2026 Answer all the questions in the spaces provided. 1 Determination of an enthalpy change of neutralisation, ∆Hneut, by thermometric titration FA 1 is 1.80 mol dm−3 sulfuric acid, H2SO4. FA 2 is aqueous sodium hydroxide, NaOH. The enthalpy change of neutralisation between an acid and an alkali can be determined using thermometric titration. This involves using a fixed volume of alkali with progressive addition of small volumes of acid and monitoring the temperature of the resulting solution. In this experiment, you are to determine the enthalpy change of neutralisation for the reaction as shown in equation 1 using thermometric titration. equation 1 1 2H2SO4(aq) + NaOH(aq) → 1 2Na2SO4(aq) + H2O(l) (a) Prepare a table in the space provided on page 4 and record, to the appropriate level of precision: • all volumes of FA 1 added, V • the maximum temperature, T, reached after each addition of acid, FA 1. It is important that the volume of FA 1 recorded is the total volume you have added up to the point when the temperature reading was made. Note: If you overshoot on an addition, record the actual total volume of FA 1 added up to that point. Procedure 1. Place one polystyrene cup inside a second polystyrene cup and place both cups in a 250 cm3 beaker. 2. Use a pipette to transfer 25.0 cm3 of FA 2 into the first polystyrene cup. 3. Fill a burette with FA 1. 4. Stir the FA 2 in the cup gently with the thermometer. Read and record its temperature. 5. Use the burette to add 5.00 cm 3 of FA 1 into the cup. Stir the mixture gently with the thermometer. Read and record both the maximum temperature and the actual total volume of FA 1 added. 6. Repeat step 5 until a total of 45.00 cm 3 of FA 1 has been added. For each addition of FA 1, read and record both the maximum temperature and the actual total volume of FA 1 added up to that point.

3 ©YIJC 9476/04/JC2/PE/2026 [Turn over Question 1 continues on the next page.

4 ©YIJC 9476/04/JC2/PE/2026 Results [3]

5 ©YIJC 9476/04/JC2/PE/2026 [Turn over (b) Plot a graph of temperature, T, on the y-axis, against total volume of FA 1, V, on the x-axis on the grid in Figure 1.1. Your scale on the y-axis should allow for extrapolation above the highest temperature recorded. Draw two lines of best -fit, taking into account the points when the temperature of the mixture was rising and the points when the temperature was falling. Each line should have a shape best suited to its plotted points. Extrapolate (extend) both lines until they intersect. Figure 1.1 [3]

6 ©YIJC 9476/04/JC2/PE/2026 (c) From your graph, read the initial temperature of FA 2, Tinitial, and the maximum temperature of the mixture, Tmax. Use these values to calculate the temperature change in the reaction, ∆T. Read the volume of FA 1 added, Vneut, at the maximum temperature of the mixture. Record all these values below. Tinitial = Tmax = ∆T = Vneut = [2] (d) (i) Calculate the heat change, q, when FA 1 has completely neutralised 25.0 cm 3 of sodium hydroxide, using the values you calculated in (c). You should assume that the specific heat capacity of the solution is 4.18 J g −1 K−1, and that the density of the solution is 1.00 g cm−3. q = [2] (ii) Determine the enthalpy change of neutralisation, ∆Hneut, for the reaction. Include the sign of ∆Hneut in your answer. ∆Hneut = [2]

7 ©YIJC 9476/04/JC2/PE/2026 [Turn over (e) Explain why the temperature , T, first increases and then decreases as the total volume of FA 1 added, V, increases. [2] (f) A student carried out the experiment and obtained a value of –60.0 kJ mol−1 for ∆Hneut. The published value for this enthalpy change is –57.0 kJ mol−1. (i) Express the difference between these two values as a percentage of the published value. [1] (ii) Explain whether the omission of heat loss to surrounding s could have been the reason for the discrepancy between the value obtained by the student and the one published. [1] [Total:16]

8 ©YIJC 9476/04/JC2/PE/2026 2 Determination of the kinetics of redox reactions Iron(III) ions can be involved in redox reactions. In this question, you will study the kinetics of the redox reaction between iron( III) ions and iodide ions, as shown in equation 2. equation 2 2Fe3+(aq) + 2I−(aq) → 2Fe2+(aq) + I2(aq) When starch is added to the reaction mixture, a blue colour is seen immediately due to the formation of an iodine–starch complex. If a small amount of sodium thiosulfate, Na2S2O3, is also present in the reaction mixture, the formation of the blue colour is delayed as the iodine , I2, produced reacts immediately with Na2S2O3, as shown in equation 3. equation 3 I2(aq) + 2S2O32−(aq) → 2I−(aq) + S4O62−(aq) When all the Na2S2O3 has reacted, the I2 which continues to be produced will turn the starch indicator blue. FA 3 is 0.0200 mol dm−3 aqueous iron(III) chloride, FeCl3. FA 4 is 0.0500 mol dm−3 aqueous potassium iodide, KI. FA 5 is 0.00500 mol dm−3 sodium thiosulfate, Na2S2O3. Solution S is starch solution. You will perform a series of three experiments. You will add a fixed amount of sodium thiosulfate, FA 5, to each of your experiments. You will add an amount of deionised water so that the total volume is 60 cm3. The time taken for the blue colour to form allows the reaction rate to be determined. (a) Fill Table 2.1 with the volume of deionised water needed in each experiment. Table 2.1 experiment FA 3 / cm3 FA 4 / cm3 FA 5 / cm3 solution S / cm3 deionised water / cm3 time, t / s 1 20.0 10.0 15.0 10.0 2 10.0 10.0 15.0 10.0 3 25.0 5.0 15.0 10.0 [4]

9 ©YIJC 9476/04/JC2/PE/2026 [Turn over Experiment 1 The end-point of the reaction is the first appearance of a blue colour. Note: Insufficient stirring of the reaction mixture may lead to a blue colour appearing before the true end-point is reached. 1. Use an appropriate measuring cylinder to transfer 10.0 cm3 of FA 4 into a 250 cm 3 beaker. Place the beaker on a white tile. 2. Using appropriate measuring cylinders, transfer to the beaker • 15 cm3 of FA 5, • 10 cm3 solution S, • appropriate volume of deionised water recorded in Table 2.1. 3. Stir the contents of the b