CCMS 2026 Sec 4 Prelim Chemistry 6092 P3 Dry Practice

[Turn over Name: Class: Class Register Number: PRELIMINARY EXAMINATION 2026 SECONDARY 4 CHEMISTRY 6092/03 Paper 3 Practical 21 August 2026 1 hour 50 minutes Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions READ THESE INSTRUCTIONS FIRST Write your name, class and register number clearly in the spaces provided 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, correction fluid or highlighters. 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 page 10. 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 2 3 Total / 40 This document consists of 10 printed pages.

2 2026 Preliminary Exam/CCHMS/Secondary 4/Chemistry/6092/03 1 In acidic conditions, potassium manganate(VII) reacts with potassium iodide to produce iodine. The iodine liberated can be titrated with aqueous sodium thiosulfate. From the titration results, the concentration of the potassium manganate(VII) can be calculated. In this experiment, you will determine the concentration of potassium manganate(VII). Read all the instructions carefully before starting the experiment in Question 1. Instructions P is potassium manganate(VII) of unknown concentration. Q is 0.1 mol/dm3 sodium thiosulfate. (a) (i) • Fill the burette with Q. • Use the pipette to transfer 25.0 cm3 of P into the conical flask. • Use the measuring cylinder to measure 10.0 cm3 of dilute sulfuric acid and add it into the conical flask. • Use the same measuring cylinder to measure 10.0 cm 3 of aqueous potassium iodide and add it into the conical flask. • Swirl the conical flask gently to mix the solutions thoroughly. The solution should turn red-brown. • Do not add the starch indicator solution at this stage. • Add Q from the burette to the conical flask until the red-brown colour fades to a pale yellow, then add a few drops of the starch indicator solution. This will give a deep blue solution. • Continue adding Q slowly from the burette, until one drop of Q causes the blue colour to disappear, leaving a colourless solution. • Record your results in an appropriate format in the space provided. Repeat the titration as many times as you consider to be necessary to achieve consistent results. Results (Titres : 25.80 cm3; 25.50 cm3; 25.30 cm3 [5] (ii) From your titration results, calculate the average volume of Q required to reach the end-point of the titration. Show clearly how you obtained this volume. average volume of Q = …………………… cm3 [1]

3 [Turn over 2026 Preliminary Exam/CCHMS/Secondary 4/Chemistry/6092/03 (b) Q is 0.1 mol/dm3 sodium thiosulfate. (i) Use your answer to (a)(ii) to calculate the amount of sodium thiosulfate, in moles, used to react with the iodine produced by the reaction of potassium manganate(VII) and potassium iodide. amount of sodium thiosulfate = ………………………. mol [1] (ii) Two moles of sodium thiosulfate react with one mole of iodine. Use your answer to (b)(i) to calculate the amount of iodine, in moles, produced by the reaction of potassium manganate(VII) and potassium iodide. amount of iodine = ………………………. mol [1] (iii) Five moles of iodine are produced by the reaction of two moles of potassium manganate(VII) with potassium iodide. Use your answer to (b)(ii) to calculate the amount, in moles, of potassium manganate(VII) used in the reaction. amount of potassium manganate(VII) = ……………………….. mol [1] (iv) Use your answer to (b)(iii) to calculate the concentration, in mol/dm 3, of the potassium manganate(VII), KMnO4, in 25.0 cm3 of solution P. concentration of KMnO4 in 25.0 cm3 of P = …………………….mol/dm3 [2]

4 2026 Preliminary Exam/CCHMS/Secondary 4/Chemistry/6092/03 (c) In this experiment, aqueous potassium iodide is added in excess. A student repeated the experiment but accidentally used insufficient aqueous potassium iodide. State and explain the effect, if any, that this would have on the volume of Q required to reach the end -point of the titration and the calculated concentration of potassium manganate(VII). ……………………...……………………………………………………………………………….. ……………………...……………………………………………………………………………….. ……………………………...……………………………………………………………………….. ……………………………………………..……………………………………………………..[2]

5 [Turn over 2026 Preliminary Exam/CCHMS/Secondary 4/Chemistry/6092/03 (d) Aqueous iron(II) sulfate also reacts with solution P. During the reaction, the purple colour of solution P disappears. Describe an experiment to investigate how the concentration of solution P affects the rate of its reaction with aqueous iron(II) sulfate. Use two different concentrations of solution P in your experiment. Your description should include: • the apparatus you would use, • the measurements you would take, and • how you would use your results to determine the effect of concentration on the rate of reaction. You may assume that all the apparatus and reagents normally found in a school laboratory are available. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. …………………………………………………………………………………………………….[6] [Total: 19]

6 2026 Preliminary Exam/CCHMS/Secondary 4/Chemistry/6092/03 2 (a) R is an aqueous mixture of two cations and one anion. (R is a mixture of copper(II) sulfate and acidified iron(II) sulfate) All the ions in R are listed in the qualitative analysis notes on page 10. Follow the instructions in Table 2.1 to carry out tests on R. You should test any gases involved. The volumes given below are approximate and should be estimated rather than measured. Record your observations in Table 2.1. If there are no observable changes, write ‘ no observable change’. Table 2.1 Test instructions observations 1 To 1 cm depth of R in a clean test-tube, add 3 drops of aqueous barium nitrate. Keep the test-tube and its contents for Test 2. 2 To the test-tube and its contents from Test 1, add 4 cm depth of aqueous ammonia. Allow the test-tube to stand for a few minutes. 3 To 1 cm depth of R in a clean test-tube, add 3 drops of aqueous silver nitrate. 4 To 1 cm depth of R in a clean test-tube, add an equal volume of aqueous hydrogen peroxide. Keep the test-tube and its contents for Test 5. 5 To the test-tube and its contents from Test 4, add 4 cm depth of aqueous ammonia. There is no need to record observations for this step. Allow the test-tube to stand for a few minutes. [8]

7 [Turn over 2026 Preliminary Exam/CCHMS/Secondary 4/Chemistry/6092/03 (b) (i) Use your observations from Table 2.1 to deduce the anion in R. Explain your answer. anion ………………………………………………………………………………………... explanation …………………………………………………………………………………. ……………………………………………………………………………………………….. [1] (ii) R contains two cations. Use your observations