2024 TMJC JC2 H2 Chemistry - Prelim P4 (QP)

1 CANDIDATE NAME CIVICS GROUP H2 CHEMISTRY 9729/04 Paper 4 Practical 27 August 2024 2 hours 30 minutes Candidates answer on the Question Paper. This document consists of 23 printed pages and 1 blank page. 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 23 and 24. The number of marks is given in brackets [ ] at the end of each question or part question. Shift Laboratory For Examiner’s Use 1 / 18 2 / 15 3 / 13 4 / 9 Total / 55 TAMPINES MERIDIAN JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION

2 Tampines Meridian Junior College 2024 JC2 Preliminary Examination H2 Chemistry Answer all questions in the spaces provided. 1 Investigation of some inorganic and organic reactions In this question, you will be investigating some inorganic and organic reactions by carrying out the stipulated tests. Carefully record your observations in Tables 1.1 and 1.2. Unless otherwise stated, the volumes given below are approximate and should be estimated rather than measured. (a) Organic analysis In this question, you will deduce the structure of an organic compound, FA 1. FA 1 has the molecular formula C4H8O2 with two functional groups present. Do not carry out the tests for which observations have been recorded. Do not use the Bunsen burner for heating in this part of the question. Instead, use the hot water provided. Table 1.1 tests observations (i) Place about 2 cm depth of aqueous sulfuric acid in a test-tube. To this test -tube, add about 1 cm depth of FA 1, followed by 1 drop of aqueous potassium manganate(VII). Warm the mixture in the hot water bath for two minutes. (ii) Add 1 cm depth of aqueous silver nitrate to a test-tube. Then slowly add 1 cm depth of aqueous sodium hydroxide. Add aqueous ammonia slowly, with shaking, until the precipitate just dissolves. To this mixture, add about 1 cm depth of FA 1. Place the test-tube containing the mixture in the water bath for two minutes. (iii) Place about 1 cm depth of FA 1 in a test -tube. To this test -tube, add 2,4 -dinitrophenylhydrazine dropwise. Orange ppt. formed (iv) Place about 1 cm depth of FA 1 and add 8 drops of aqueous sodium hydroxide in a test -tube. Then, add aqueous iodine dropwise, until a permanent yellow / orange colour is obtained. Warm the mixture in the hot water bath for two minutes. (v) Place 1 cm depth of FA 1 in a test-tube. To this test-tube, cautiously add a small piece of anhydrous phosphorus pentachloride. Dense white fumes, which turns moist blue litmus paper red. [2] M1 M2

3 Tampines Meridian Junior College 2024 JC2 Preliminary Examination H2 Chemistry [Turn Over (b) (i) Observations from (a)(ii) and (a)(iii) can be used to identify one of the functional groups present in FA 1. Identify the functional group and explain your answer, showing clearly your reasoning. functional group: explanation: [1] (ii) Using observations from either ( a)(iv) or (a)(v), identify the other functional group present in FA 1. Quote evidence from the relevant test to support your conclusion. functional group: evidence: [1] (iii) Suggest a possible structure of FA 1 that are consistent with all the observations in Table 1.1. [1] M3 M4 M5

4 (c) Inorganic analysis FA 2 is an aqueous solution containing Fe3+. FA 3 contains one cation and FA 4 contains one anion listed in the Qualitative Analysis Notes on pages 23 – 24. You should indicate clearly at what stage in a test a change occurs. Test and identify any gases evolved. If there is no observable change, write no observable change. 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 precipitate in an excess of the reagent added No additional tests for ions present should be attempted. Table 1.2 tests observations (i) Test the FA 2 solution using Universal Indicator paper. (ii) To 1 cm depth of FA 2, add 1 cm depth of hydrochloric acid followed by a small spatula of zinc powder. Shake well. Leave the mixture to stand for five minutes. (iii) To 1 cm depth of FA 2, add a few drops of aqueous sodium thiosulfate with shaking. Leave the mixture to stand. [2] M6 M7

5 Tampines Meridian Junior College 2024 JC2 Preliminary Examination H2 Chemistry [Turn Over tests observations (iv) To 1 cm depth of FA 3, add an equal volume of aqueous potassium iodide, then add aqueous sodium thiosulfate dropwise with shaking until no further change is observed. (v) To 1 cm depth of FA 3, add aqueous ammonia slowly, with shaking, until no further change is seen. [3] (d) (i) Explain your observations in (c)(i), given that the cation present in FA 2 is Fe3+. [1] (ii) State the type of reaction that is likely to have occurred in (c)(iii). [1] (iii) Identify the cation present in FA 3. Use evidence from your observations in 1(c) to support your deduction. cation: evidence: [1] M8 M9 M10 M11 M12 M13

6 Tampines Meridian Junior College 2024 JC2 Preliminary Examination H2 Chemistry (iv) Write an ionic equation to account for the observations made for the first reaction in (c)(iv). Include state symbols. [1] (e) Devise and perform a series of three simple tests to identify the anion in FA 4. Your tests should be based on the Qualitative Analysis Notes on pages 23 – 24 and should use only the bench reagents provided. Record your tests and observations in the space below. Any test requiring heating MUST be performed in a boiling tube. The anion is not a nitrite, sulfate or sulfite ion. [3] Use your observations above to deduce the identity of the anion in FA 4. anion: [1] M14 M15 M16 M17 M18 [Total: 18]

7 Tampines Meridian Junior College 2024 JC2 Preliminary Examination H2 Chemistry [Turn Over 2 Determination of the kinetics of the reaction between iron(III) and iodide ions You are provided with the following reagents. FA 5 is an acidified solution of aqueous iron(III) chloride, FeCl3. FA 6 is aqueous potassium iodide, KI. FA 7 is 0.0060 mol dm−3 sodium thiosulfate, Na2S2O3. starch solution In an acidic medium , i ron(III) ions, Fe 3+ oxidises iodide ions, I–, to iodine, I2 as shown in equation 1. equation 1 2Fe3+(aq) + 2I−(aq) → 2Fe2+(aq) + I2(aq) It is possible to determine the rate of this reaction by measuring the time to produce a certain amount of iodine. To do this, a fixed and small amount of thiosulfate ions, S 2O32–, and starch indicator are added to the reaction mixture. The thiosulfate ions react immediately with the iodine produced by the reaction and convert it back to iodide ions as shown in equation 2. equation 2 2S2O32−(aq) + I2(aq) → S4O62−(aq) + 2I−(aq) The reaction in equation 2 stops once all the thiosulfate ions have reacted. The concentration of iodine now increases and is detected by starch indicator in the reaction mixture, which causes th