TJC 2026 H2 Chemistry Prelims Paper 4 Ans

9476 / TJC Prelim / 2026 [Turn Over TEMASEK JUNIOR COLLEGE 2026 JC2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS CENTRE NUMBER S INDEX NUMBER Chemistry 9476/04 Paper 4 Practical 27 August 2026 2 hours 30 minutes Candidates answer on the Question Paper. READ THESE INSTRUCTIONS FIRST Write your name, CG, centre number and index number on all the work you hand in. 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 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 pages 18 to 20. 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. This document consists of 20 printed pages. For Examiner’s Use 1 2 3 4 Total Shift Laboratory

2 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 9476 / TJC Prelim / 2026 Answer all the questions in the spaces provided. 1 Qualitative analysis At each stage of any test you are to record details of the following: • colour changes seen • the formation of any precipitate • the solubility of such precipitates in an excess of the reagent added. Test and identify any gases evolved. You should indicate clearly at what stage in a test a change occurs. No additional tests for ions present should be attempted. Rinse and reuse test-tubes and boiling tubes where possible. (a) FA 1 is a mixture of two salts, each of which contains a single cation and a single anion from those listed in the Qualitative Analysis Notes on pages 18 to 20. Do the following tests and record your observations in Table 1.1 below. 2[✓] = 1 mark Table 1.1 test observations (i) Place a small spatula of FA 1 in a test-tube. Carefully add dilute sulfuric acid until the reaction is complete. ➔ Test for gas Effervescence and colourless CO2 gas forms white ppt with limewater ✓ Light blue solution obtained ✓ Then add aqueous sodium hydroxide with shaking, until the aqueous sodium hydroxide is in excess. ➔ Test for cation blue ppt formed and is insoluble in excess NaOH ✓ (ii) To a 3 cm depth of deionised water in a boiling tube, add the remaining sample of FA 1. Stir and then filter the mixture into a clean boiling tube. You will use this solution for tests (iii) – (v).

3 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 9476 / TJC Prelim / 2026 [Turn over (iii) Add 1 cm depth of the solution from (ii) into a clean test-tube. Add aqueous sodium hydroxide slowly, until the aqueous sodium hydroxide is in excess. ➔ Test for cation white ppt formed and is insoluble in excess NaOH ✓ (iv) Add 1 cm depth of the solution from (ii) into a clean test-tube. Add aqueous ammonia slowly, until the aqueous ammonia is in excess. ➔ Test for cation white ppt formed and is insoluble in excess NaOH ✓ Then add a spatula full of ammonium chloride. white ppt soluble in excess NH4Cl to give a colourless solution.✓ (v) Add 1 cm depth of the solution from (ii) into a clean test-tube. Add 1 cm depth of aqueous barium nitrate. Add dilute nitric acid until the nitric acid is in excess. ➔ Test for sulfate/sulfite white ppt formed ✓ white ppt is insoluble in excess HNO3 ✓ [4] (vi) Complete Table 1.2 to identify the cations and anions present in FA 1. Table 1.2 FA 1 Cations present Anions present [2]

4 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 9476 / TJC Prelim / 2026 2[✓] = [1] FA 1 Cations present Cu2+✓ Mg2+✓ Anions present CO32−✓ SO42−✓ (vii) With the aid of an equation, explain your observation in part (a)(i) that allows you to identify one of the cations. [1] Blue ppt of Cu(OH)2 formed with NaOH(aq) ✓ and insoluble in excess NaOH(aq) suggest the presence of Cu2+. Cu2+ + 2OH– → Cu(OH)2 ✓ 2[✓] = [1] (viii) Give one reason why it is necessary to perform (a)(ii) before (a)(iii) and (a)(iv). [1] To separate Mg 2+ from Cu 2+ so that the white ppt, Mg(OH) 2, formed using NaOH and aq. NH3 can be easily observed. [1]

5 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 9476 / TJC Prelim / 2026 [Turn over (b) Organic analysis FA 2, FA 3 and FA 4 are aqueous solutions of organic compounds. All FA 2, FA 3 and FA 4 contain carbon, hydrogen and oxygen only and they each contain one type of functional group. You will carry out tests to identify the functional group s present in FA 2, FA 3 and FA 4 and to deduce the structure of FA 2 and FA 4. (i) Perform the tests described in Table 1.3. Some of the observations have been completed for you. There is no need to carry out these tests. R ecord your observations in Table 1.3. Test and identify any gases evolved. If there is no observable change, write no observable change. When organic solutions are to be heated, a hot water bath should be used. Table 1.3 test observations FA 2 FA 3 FA 4 1 Add 1 cm depth of the FA solution in a test - tube. Add a small spatula of sodium carbonate to the test-tube. ➔ Test for COOH via CO2 gas evolved Effervescence and Colourless CO2 gas forms white ppt with limewater ✓ Effervescence and Colourless CO2 gas forms white ppt with limewater ✓ no observable change ✓ or no effervescence 2 Add 1 cm depth of the FA solution in a test - tube. Add 5 cm depth of 2,4- dinitrophenylhydrazine solution to the test - tube. no observable change no observable change orange precipitate observed 3 Add a few drops of the FA solution in a test - tube. Add a spatula of PC l5 to the test-tube. white fumes observed white fumes observed no observable change

6 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 9476 / TJC Prelim / 2026 4 Add 1 cm depth of the FA solution in a test - tube. Add 15 drops of dilute sulfuric acid followed by 1 drop of acidified potassium manganate(VII). Place the test -tube in the hot water bath and leave to stand. Purple KMnO4 decolourises ✓ no observable change ✓ or purple KMnO4 remained Purple KMnO4 decolourises ✓ 3[✓] = [1] [2] (ii) Using your observations from Table 1.3, deduce the functional group present in both FA 2 and FA 3. [1] Carboxylic acid since both undergo acid-base reaction with Na2CO3 as effervescence was seen in test 1. [1] (iii) Hence, suggest a possible structure of FA 2 that is consistent with all the observations in Table 1.3. [1] HCO2H [1] accept (COOH)2 FA 2 is a carboxylic acid that can be further oxidised. (iv) The relative molecular mass of FA 4 is determined to be 58.0. Using your observations from Table 1.3, suggest the structure of FA 4. Give evidence to support your conclusion. [Ar: H, 1.0; C, 12.0; O, 16.0] [1] CH3CH2CHO. Orange ppt is formed in test 2 and purple KMnO 4 decolourised in test 4. Hence FA 4 is an aldehyde since it can undergo condensation reaction with 2,4-DNPH and can undergo oxidation with KMnO4. [1] Mentioning of only one reaction will not gain this mark. [Total: 13]

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