HCI 2024 Prelim P4 QP

This document consists of 16 printed pages. HWA CHONG INSTITUTION C2 Preliminary Examination Higher 2 CANDIDATE NAME CT GROUP 2 3 S CENTRE NUMBER S INDEX NUMBER CHEMISTRY Paper 4 Practical 9729/04 20 August 2024 2 hours 30 minutes Candidates answer on the Question Paper. READ THESE INSTRUCTIONS FIRST Write your name, CT group, 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 a HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE ON ANY BARCODES. 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 15 and 16. 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 Shift Laboratory For Examiner’s Use 1 2 3 4 Total

2 © Hwa Chong Institution 2024 9729/04/C2 Preliminary Examination Answer all questions in the spaces provided. 1 Qualitative Analysis of FA 1 FA 1 is an aqueous solution containing two cations & one anion. FA 2 is hydrogen peroxide. You will perform tests to identify the cations and anion in FA 1. Unless otherwise stated, the volumes given are approximate and should be estimated rather than measured. 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 Where gases are released, they should be identified by a test, described in the appropriate place in your observations. You should indicate clearly at what stage in a test a change occurs. No additional tests for ions present should be attempted. (a) (i) Carry out the following tests. Carefully record your observations in Table 1.1. Table 1.1 Note: Observations to test 1 have been recorded for you. MMO M test observations 1 To 1 cm depth of FA 1 in a test-tube, add one spatula full of solid sodium carbonate. Effervescence of colourless and odourless gas that gives white ppt in limewater. White ppt observed after effervescence ceased. 2 Place 1 cm depth of FA 1 in a boiling tube using a dropping pipette. Measure 6 cm3 of aqueous sodium hydroxide with a measuring cylinder. Transfer 1 cm3 of aqueous sodium hydroxide to FA 1 in the boiling tube using a dropping pipette. Mix the contents of the tube thoroughly. Repeat this with another 1 cm3 of aqueous sodium hydroxide. Repeat until the measuring cylinder is empty.

3 © Hwa Chong Institution 2024 9729/02/C2 Preliminary Examination Filter the mixture into a clean test- tube using a filter funnel. While waiting, proceed to test 3. Transfer 1 cm depth of the filtrate to a test-tube and add dilute sulfuric acid (FA 4) dropwise until no further changes are seen. If the earlier filtration is not completed, carefully decant the remaining liquid into the sink. Wash the residue by adding deionised water to the filter funnel until it is around half full. Wait for around one minute before carefully decanting the remaining liquid into the sink. Retain the residue for use in (b). 3 To 1 cm depth of FA 1 in a test-tube, add aqueous ammonia, dropwise with shaking. Continue adding aqueous ammonia until no further changes are seen. Leave the test-tube to stand. 4 To 1 cm depth of FA 1 in a test-tube, add 1 cm depth of aqueous Ba(NO3)2. Add dilute HNO3 to the above. [6] ACE M (ii) Identify the two cations and one anion in FA 1. For each ion, complete Table 1.2 by stating evidence from tests 2 to 4. Table 1.2 cation evidence

4 © Hwa Chong Institution 2024 9729/04/C2 Preliminary Examination anion evidence [3] ACE H (iii) Based on the given observations in test 1, describe the types of reaction that occurred and identify any new substances formed. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. …………………………………………………………………………………………………….[2] MMO (b) (i) Carry out the following tests on the residue from test 2 in 1(a). H test observations Place the filter funnel with the washed residue from (a) over a clean test-tube. Carefully add dilute HNO3 to the filter funnel until it is around half full. Collect around 1 cm depth of the filtrate. To the 1 cm depth of the filtrate in the test-tube, add 1 cm depth of FA 2. Then, add aqueous sodium hydroxide drop by drop carefully, with shaking, until no further changes are seen. [3] ACE (ii) By considering your observations in 1(b)(i), explain how the addition of aqueous sodium hydroxide affects the reaction involving FA 2. H ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. …………………………………………………………………………………………………….[1] [Total: 15]

5 © Hwa Chong Institution 2024 9729/02/C2 Preliminary Examination 2 To study the kinetics of the reaction between potassium manganate(VII) and ethanedioic acid in the presence of FA 1 You are provided with the following. FA 3 is 0.100 mol dm−3 potassium iodide. FA 4 is 1.00 mol dm–3 sulfuric acid. FA 5 is 0.0050 mol dm−3 sodium thiosulfate. FA 6 is 0.0200 mol dm−3 potassium manganate(VII). FA 7 is 0.200 mol dm−3 ethanedioic acid. Solution I is starch indicator. Manganate(VII) ions react with ethanedioate ions in acidic solution as follows. 2MnO4–(aq) + 5C2O42–(aq) + 16H+(aq) → 2Mn2+(aq) + 10CO2(g) + 8H2O(l) reaction 1 Part I You will prepare a reaction mixture containing potassium manganate( VII), ethanedioic acid, sulfuric acid and FA 1. At suitable time intervals, you will withdraw aliquots of the reaction mixture and add them to potassium iodide solution (in excess). The MnO 4– ions (remaining in each aliquot at that time) react with iodide ions as follows. 2MnO4–(aq) + 10I–(aq) + 16H+(aq) → 2Mn2+(aq) + 5I2(aq) + 8H2O(l) reaction 2 You will then titrate the iodine produced against sodium thiosulfate solution, and the reaction is as follows. 2S2O32–(aq) + I2(aq) → S4O62–(aq) + 2I–(aq) reaction 3 You will analyse the results using a graph of volume of sodium thiosulfate against time. PDO MMO L (a) You are advised to study this entire series of steps before starting your experiment. You are also advised to manage your time effectively so that you can complete all the titrations and the question parts in the next few pages. Measuring and filling of FA 3 and FA 5 1 Use a measuring cylinder to add about 10 cm3 of FA 3 into each of the five labelled boiling tubes. 2 Fill a burette with FA 5. Preparation of reaction mixture and withdrawing aliquots 3 Use separate measuring cylinders to add the following into the conical flask labelled 'reaction mixture'. • 48.0 cm3 of deionised water • 50.0 cm3 of FA 7 • 5.0 cm3 of FA 4 • 2.0 cm3 of FA 1

6 © Hwa Chong Institution 2024 9729/04/C2 Preliminary Examination 4 Use another measuring cylinder to measure 2 0.0 cm 3 of FA 6. Add this FA 6 into the mixture prepared in step 3, immediately starting the stopwatch when the two liquids contact. Swirl the reaction mixture thoroughly. 5 At approximately 1 minute, withdraw a 10.0 cm3