TMJC 2023 H2 Chem P4 QP

Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Chemistry CANDIDATE NAME CIVICS GROUP H2 CHEMISTRY 9729/04 Practical 29 August 2023 2 hours 30 minutes Candidates answer on the Question Paper. This document consists of 21 printed 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 20 and 21. The number of marks is given in brackets [ ] at the end of each question or part question. Shift Laboratory For Examiner’s Use 1 / 11 2 / 16 3 / 17 4 / 11 Total / 55 TAMPINES MERIDIAN JUNIOR COLLEGE PRELIMINARY EXAMINATION

2 Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Chemistry Answer all the questions in the spaces provided. 1 Investigation of organic and inorganic compounds (a) FA 1 , FA 2 , FA 3 and FA 4 are aqueous solutions known to be hydrochloric acid, ethanoic acid, methanoic acid and sulfuric acid. All the solutions have the same concentration. Note: the order of FA 1 to FA 4 does not correspond to the order of identities given above. (i) Carry out the following tests for FA 1 to FA 3. Record your observations in Table 1.1. Observations for FA 4 have already been recorded in Table 1.1. There is no need to carry out the tests for FA 4. The volumes given below 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.

[Turn over 3 Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Chemistry Table 1.1 test observations FA 1 FA 2 FA 3 FA 4 1. Add about 2 cm depth of FA 1 in a test-tube. Add a piece of magnesium into FA 1. Repeat using FA 2 and FA 3, in place of FA 1. There is slower effervescence observed. Gas evolved “pops” with a lighted splint. Gas is hydrogen. 2. To a 1 cm depth of dilute sulfuric acid in a test-tube, add 2 drops of aqueous potassium manganate(VII). Then add 2 cm depth of FA 1. Place the test-tube in a hot water bath. Repeat using FA 2 and FA 3, in place of FA 1. No observable change. [3] M1 M2 M3

4 Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Chemistry (ii) Complete Table 1.2 with the identities of FA 3 and FA 4. Give evidence from the observations in Table 1.1 to support your conclusio ns. Table 1.2 identity evidence FA 3 FA 4 [2] (iii) Carry out one additional test that allows you to distinguish between FA 1 and FA 2. Your tests should be based on the Qualitative Analysis Notes on pages 20–21 and should use only the bench reagents provided. Record your tests and observations in the space below. FA 1 is ………………………………. FA 2 is ………………………………. [2] M4 M5 M6 M7

5 Tampines Meridian Junior College 2023 Preliminary Examination H2 Chemistry [Turn over (b) In this question, you will investigate the chemistry of vanadium ions. FA 5 contains vanadate(V) ions, VO3  . When FA 5 is acidified and reacted with a metal M, a series of colour changes can be observed during the reaction. You will carry out tests to study the reaction of acidified FA 5 with the metal M. Record your observations in Table 1.3. In these reactions, you do not need to test for any gas that is evolved. Table 1.3 Tests Observations (i) Place 2 cm depth of FA 5 into a boiling tube. Add 4 cm depth of sulfuric acid to the same boiling tube . Mix well and record any colour changes that occur. (ii) Using a spatula, add metal M, a very small amount (about half spatula) at each time, into the boiling tube. Swirl after each addition. You are required to make 4 additions of metal M. Note: it is important to add M in small amounts in order to obtain accurate observations. You may leave the mixture to stand, swirling the boiling tube from time to time and observe the solution until no further changes are seen. While you are waiting, continue with the other questions. [2] M8 M9

6 Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Chemistry (c) The half equations that represent the stepwise reduction of VO3  ions are shown below. Electrode reaction E / V VO3  + 4H+ + e ⇌ VO2+ + H2O +1.00 VO2+ + 2H+ + e ⇌ V3+ + H2O +0.34 V3+ + e ⇌ V2+ 0.26 V2+ + 2e ⇌ V 1.20 The ions VO2+, V3+ and V2+ have different colours. A student suggested that metal M could be platinum, silver or zinc. [E Pt2+/Pt = +1.18 V; E Ag+/Ag = +0.80 V; E Zn2+/Zn = −0.76 V)] With reference to the E values and your observations in test (ii) of Table 1.3, give two reasons why metal M is likely to be zinc. [2] [Total: 11] M10 M11

7 Tampines Meridian Junior College 2023 Preliminary Examination H2 Chemistry [Turn over 2 Investigation of the effect of concentration on rate of reaction In acidic solutions, iron(III) ions oxidise iodide ions, I−, to iodine, I2. 2Fe3+(aq) + 2I−(aq)  2Fe2+(aq) + I2(aq) The rate of this reaction can be investigated by using starch indicator, which turns blue ‑black in the presence of iodine. Sodium thiosulfate is added to the reaction mixture to react with iodine as it is formed. The blue-black colour is seen when all the thiosulfate has reacted. I2(aq) + 2S2O3 2−(aq)  2I−(aq) + S4O6 2−(aq) You will investigate how the rate of reaction is affected by changing the concentration of the iodide ions. FA 6 is 0.0500 mol dm–3 potassium iodide, KI. FA 7 is 0.0500 mol dm–3 acidified iron(III) chloride, FeCl3. FA 8 is 0.00500 mol dm–3 sodium thiosulfate, Na2S2O3. FA 9 is starch indicator. You should read through the whole method before starting any practical work. (a) Method Experiment 1  Fill a burette with FA 6.  Run 20.00 cm 3 of FA 6 into a 100 cm3 beaker and place it on a white tile.  Use a 50.0 cm3 measuring cylinder to add the following to the same 100 cm3 beaker: o 20 cm 3 of FA 8 o 10 cm 3 of FA 9  Use the 10 cm3 measuring cylinder labelled FA 7 to measure 10.0 cm3 of FA 7.  Add this FA 7 into the same 100 cm3 beaker and start timing immediately.  Stir the mixture once with a glass rod.  Stop timing as soon as the solution turns blue ‑black. Ignore any colour changes that occur before the intense blue‑black colouration.  Record this reaction time to the nearest second in Table 2.1.  Wash out the beaker and dry it with a paper towel. Rinse and dry the glass r od. Experiment 2  Run 10.00 cm 3 of FA 6 into the 100 cm3 beaker.  Use a second 10.0 cm 3 measuring cylinder to add deionised water into the beaker containing FA 6.  Use the 50.0 cm3 measuring cylinder to add the following to the same 100 cm3 beaker: o 20 cm 3 of FA 8 o 10 cm 3 of FA 9  Use the 10 cm3 measuring cylinder labelled FA 7 to measure 10.0 cm3 of FA 7.  Add this FA 7 into the same 100 cm3 beaker and start timing immediately.  Stir the mixture once with a glass rod.  Stop timing as soon as the solution turns blue ‑black.