NJC 2026 H2 Chemistry Prelim P4 answer

1 NJC SH2 Preliminary Examination 9476/04/26 NATIONAL JUNIOR COLLEGE SH 2 Prelim Practical Examination Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 4 Practical You must answer on the question paper. 9476/04 Monday 1 September 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 identification number and name. • 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 paper consists of 20 pages. Any blank pages are indicated. Shift Laboratory For Examiner’s use 1 / 7 2 / 8 3 / 10 4 / 17 5 / 8 Total / 50

2 NJC SH2 Preliminary Examination 9476/04/26 1 Inorganic Qualitative Analysis FA 1 is a solution which contains two cations and two anions. Perform the tests described in Table 1.1 and record your observations in the table. Test and identify any gases evolved. For Examiner’s Use Table 1.1 tests observations (a) (i) To a 2 cm depth of FA 1 solution in a test tube, add aqueous sodium hydroxide, slowly with shaking, until 4 cm depth of aqueous sodium hydroxide is added. Gently warm the mixture. Then filter the mixture, collecting the filtrate in a clean test-tube. Leave to stand for several minutes. Keep the filtrate for test (ii) and (iii). FA 1 is yellow in colour Green ppt insoluble in excess NaOH. (✓) (colourless and pungent) gas turns damp red litmus paper blue. (✓) gas is NH3 (✓) [If no gas, must write “moist litmus paper remain red”] green residue (✓) which turns red-brown on contact with air/ on standing (✓) and colourless/ pale yellow filtrate (✓) (ii) To a 1 cm depth of the filtrate from test (i) in a test -tube, add barium nitrate dropwise. Then add dilute hydrochloric acid until there is no further change. White ppt. (✓) ppt. insoluble in excess dilute hydrochloric acid. (✓) [If no ppt, must write “no ppt”] (iii) To a 1 cm depth of the filtrate from test (i) in a test-tube, add 1 cm depth of aqueous silver nitrate. Add aqueous ammonia to the mixture, with shaking until there is no further change. White ppt. (✓) ppt. soluble in excess NH3(aq). (✓) [If no ppt, must write “no ppt”] [5]

3 NJC SH2 Preliminary Examination 9476/04/26 [Turn over (b) By considering the observations made in Table 1.1 and making reference to the Qualitative Analysis Notes, iidentify the cations and the anions present in FA 1. The cations in FA 1 are Fe2+ and NH4+ The anions in FA 1 are SO42- and Cl- [2] [Total: 7] 2 Organic Qualitative Analysis In this question, you will deduce the structure of an organic compound, FA 2 . The molecular formula of FA 2 is C5H10O2. Perform the tests described in Table 2.1, and record your observations in the table. Test and identify any gases evolved. Some observations have been recorded. Some observations have been recorded in part (b). Do not use Bunsen burner for heating. Use the hot water provided. Table 2.1 tests observations (a) (i) Place about 2 cm depth of aqueous sulfuric acid in a test-tube. To this test -tube, add 10 drops of FA 2, followed by 1 drop of aqueous potassium manganate(VII). Warm the mixture in the hot water bath for two minutes. Purple KMnO4 turns colorless. (ii) Place about 2 cm depth of aqueous silver nitrate in a test-tube. To this test -tube, add 10 drops of aqueous sodium hydroxide, followed by aqueous ammonia until a clear solution is formed. To this test -tube, add 10 drops of FA 2. Warm the mixture in the water bath for two minutes. Brown ppt. dissolves in NH3(aq) to give a colourless solution. Not a marking point No silver mirror/ absence of grey ppt (iii) Place about 1 cm depth of deionised water in a test-tube. To this test-tube, add 10 drops of FA 2 and add 1 5 drops of aqueous sodium hydroxide. Now add iodine solution dropwise, until a permanent orange colour is obtained. Pale yellow ppt. formed. ½ m for each correct answer

4 NJC SH2 Preliminary Examination 9476/04/26 Warm the mixture in the water bath for two minutes. [3] (b) (i) When sodium metal and 2,4-dinitrophenylhydrazine are added to separate samples of FA 2, effervescence extinguishes a lighted splint with a “pop” sound and an orange precipitate is observed respectively. Use this information and the observations recorded in table 2.1, identify two functional groups present in FA 2. Give evidence(s) to support your conclusion. Functional group: ketone Evidence: It undergoes condensation with 2,4-dinitrophenylhydrazine / It gives an orange ppt with 2,4-dinitrophenylhydrazine. AND It is not oxidised by Tollens’ reagent / no silver mirror in test (ii). [2] Functional group: 1o or 2o alcohol (award one for either) Evidence: It is oxidised by purple KMnO4 / purple KMnO4 is decolorised in test (i) It undergoes a redox reaction with Na / it gives H2 gas with Na. [2] (ii) Suggest a structure of FA 2 given that it contains a chiral centre. OOH O OH O OH OR OR OH O OR [1] [Total: 8]

5 NJC SH2 Preliminary Examination 9476/04/26 [Turn over 3 Determination of the volume strength of hydrogen peroxide The concentrations of solutions of hydrogen peroxide are often represented in terms of ‘volume strength’. In this experiment you will determine the ‘volume strength’ of a solution of hydrogen peroxide by titration with acidified potassium manganate(VII). 2MnO4–(aq) + 5H2O2(aq) + 6H+(aq) → 2Mn2+(aq) + 8H2O(l) + 5O2(g) FA 3 is 0.0300 mol dm–3 potassium manganate(VII), KMnO4. FA 4 is aqueous hydrogen peroxide, H2O2. FA 5 is 1.0 mol dm–3 sulfuric acid, H2SO4. (a) (i) Dilution of FA 4 • Pipette 25.0 cm3 of FA 4 into the 250 cm3 volumetric flask. • Make the solution up to the mark using deionised water. • Label this solution of hydrogen peroxide FA 6. This is a solution of hydrogen peroxide suitable for titration. Keep FA 5 and FA 6 for use in Question 4. Titration of FA 6 against FA 3 1. Fill the burette with FA 3. 2. Pipette 25.0 cm3 of FA 6 into a conical flask. 3. Use the 50 cm3 measuring cylinder to add 20.0 cm3 of FA 5 into the same conical flask. 4. Run FA 3 from the burette into the flask. The end-point is reached when the first permanent pink is observed. 5. Record your titration results, to an appropriate level of precision, in the space provided below. 6. Discard the reaction mixture. 7. Repeat steps 2 to 6 until consistent results are obtained. Titration results Initial burette reading/ cm3 1.00 40.70 Final burette reading/ cm3 21.70 20.00 Volume of FA 3 used/ cm3 20.70 20.70 1m for correct header and units and data recorded to correct precision 1m for initial burette reading < final burette reading and correct calculation of consistent titre values. 2m for accuracy: within  0.20 cm3 = 2m within  0.