TMJC 2025 H2 Chem P4 QP

CANDIDATE NAME CIVICS GROUP H2 CHEMISTRY 9729/04 Paper 4 Practical 3 September 2025 2 hours 30 minutes Candidates answer on the Question Paper. This document consists of 19 printed pages and 3 blank pages. READ THESE INSTRUCTIONS FIRST Write your name and Civics Group in the spaces at the top of the 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 or correction fluid. Answer all questions in the spaces provided on the question paper. The use of an approved 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 21 and 22. The number of marks is given in brackets [ ] at the end of each question or part question. Shift Laboratory For Examiner’s Use 1 / 10 2 / 19 3 / 17 4 / 9 Total / 55 TAMPINES MERIDIAN JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION

2 Tampines Meridian Junior College 2025 JC2 Preliminary Examinations H2 Chemistry Answer all questions in the spaces provided. 1 Qualitative analysis tests involving solid iron(III) chloride FA 1 is a solution containing iron(III) chloride, FeCl3.nH2O FA 2 is a solution containing an unknown L– ligand Carry out the following tests. Record your observations in Table 1.1. Unless otherwise stated , the volumes given in Table 1.1 are approximate and should be estimated rather than measured. Test and identify any gases evolved. If there is no observable change, write no observable change. Table 1.1 Test Observations (a) (i) Add about 6 cm depth of FA1 into a test tube. Add aqueous silver nitrate in excess. Filter the mixture. Separate the filtrate into four test tubes for (iii), (iv), (v) and (vi). (ii) Place the filter funnel containing the residue on a new test tube, add aqueous ammonia over the residue and collect the filtrate. To this filtrate, add nitric acid dropwise until no further changes. (iii) To the first test tube containing the filtrate from (i), add 2 cm3 of hydrogen peroxide. Observe the mixture until no further changes are seen.

3 Tampines Meridian Junior College 2025 JC2 Preliminary Examination H2 Chemistry [Turn Over (iv) To the second test tube containing the filtrate from (i), add an equal volume of aqueous sodium hydroxide. Then add 2 cm3 of hydrogen peroxide. Observe the mixture until no further changes are seen. (v) To the third test tube containing the filtrate from (i), add 1 cm3 of FA 2. (vi) To the last test tube containing the filtrate from (i), add half a spatula of iron filings. Then add an equal volume of hydrochloric acid. Dispose the reaction mixture once observations are completed to prevent gas build up. [5] (b) (i) With the aid of the following equilibrium equations, explain the observations obtained in Test (ii) when nitric acid was added to the filtrate. AgCl(s) Ag+(aq) + Cl–(aq) -- Equilibrium 1 Ag+(aq) + 2NH3(aq) [Ag(NH3)2]+(aq) -- Equilibrium 2 ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ……………………………………………………………………………………………….. [1]     M1 M2 M3 M4 M5 M6

4 Tampines Meridian Junior College 2025 JC2 Preliminary Examinations H2 Chemistry (ii) In the presence of a strong base, hydrogen peroxide reacts with OH – to form HO2–. electrode reaction EƟ/V Fe3+ + e– ⇌ Fe2+ +0.77 Fe(OH)3 + e– ⇌ Fe(OH)2 + OH– –0.56 O2 + 2H+ + 2e– ⇌ H2O2 +0.68 H2O2 + 2H+ + 2e– ⇌ 2H2O +1.77 O2 + H2O + 2e– ⇌ HO2– + OH– –0.08 With reference to the electrode potential given above, calculate the overall E Ɵ values for the reactions in Tests (iii) and (iv) respectively. Hence, account for the difference in the rate of effervescence produced when hydrogen peroxide was added in Tests (iii) and (iv). ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… …………….………………………………………………………………………….……… [2] (iii) Based on your observation in Test (v), state the type of reaction that has occurred. ………………………………………………………………..…………………………...…. [1] (iv) In Test (vi), a comproportionation reaction occurred, where two species of the same element undergoes a redox reaction to form the same product. Write an ionic equation to represent the reaction. ………………………………………………………………..…………………………...…. [1] [Total: 10] M7 M8 M9 M10

5 Tampines Meridian Junior College 2025 JC2 Preliminary Examination H2 Chemistry [Turn Over 2 Determination of water of crystallisation in a hydrated iron(III) salt Iron(III) chloride solutions are often used as a coagulant to remove impurities in sewage and industrial waste. FA 3 is hydrated iron(III) chloride with the formula FeCl3.nH2O. The addition of excess zinc to a solution of FA 3 converts the Fe3+ ions to Fe2+ ions. The amount of Fe2+ ions can then be determined quantitatively by titration against a standard solution of potassium manganate(VII), KMnO4. The reaction between MnO4− and Fe2+ is as shown below. 5Fe2+ + MnO4− + 8H+ 5Fe3+ + Mn2+ + 4H2O In this experiment, you are to prepare a standard solution using FA 3 and perform titrations to determine the value of n, the water of crystallisation in FA 3. You are provided with the following: FA 3 is solid hydrated iron(III) chloride, FeCl3.nH2O FA 4 is 0.500 mol dm-3 dilute sulfuric acid, H2SO4 FA 5 is 0.0200 mol dm−3 potassium manganate(VII), KMnO4 Zinc powder (a) Preparation of standard solution of hydrated iron(III) salt 1. Weigh the capped container with FA 3. Record the mass. 2. Transfer all the FA 3 measured into a 250 cm 3 beaker. Reweigh the weighing bottle and record its mass. Determine and record the mass of FA 3 transferred. 3. Use a 100 cm 3 measuring cylinder to add 100 cm 3 of FA 4 to the beaker. Stir the mixture with a glass rod to dissolve all the solid. 4. Transfer the solution into a 250 cm3 volumetric flask. Rinse the beaker with deionised water and pour the washings into the volumetric flask. 5. Make up to the 250 cm 3 mark with deionised water, stopper and mix thoroughly by inverting the flask several times. 6. Label the resultant solution FA 6. (b) Preparation of Fe2+ solution from FA 6 7. Use a 100 cm3 measuring cylinder to transfer 100 cm3 of FA 6 into a 250 cm3 beaker. 8. Add all the zinc powder in the container into the beaker. Continuously stir the reaction mixture for 5 minutes. 9. Filter the mixture into a dry 250 cm3 conical flask provided using dry filter paper and filter funnel. Ignore any reaction that may still be taking place. 10. Label the filtrate as FA 7. Proceed to (c) once you have collected sufficient filtrate. ⎯⎯ →

6 Tampines Meridian Junior College 2025 JC2 Preliminary Examinations H2 Chemistry (c) Titration of FA 7 against FA 5 11. Fill the burette with FA 5 solution. 12. Use a 10 cm3 pipette to transfer 10.0 cm3 of FA 7 into a 250 cm3 conical flask. 13. Use a 10 cm3 measuring cylinder to add 10.0 cm3 of FA 4 to this flask. 14. Titrate the reaction mixture in the conical flask with FA 5 from the burette until the appearance of the first permanent orange colour. 15. Record your titration results, to an appropriate level of precision, in the space below. 16. Repeat steps 12 to 15 until consistent results are obtained. Results [4] M11 M12