2025 Prelim P4 QP (for exchange) H2 Chem HCI

This document consists of 17 printed pages and 1 blank page. HWA CHONG INSTITUTION C2 Preliminary Examination Higher 2 CANDIDATE NAME CT GROUP 2 4 S CENTRE NUMBER S INDEX NUMBER CHEMISTRY Paper 4 Practical 9729/04 26 August 2025 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 an 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 17 and 18. 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 Total

2 © Hwa Chong Institution 2025 9729/04/C2 Preliminary Examination DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN Answer all questions in the spaces provided. 1 (a) Qualitative Analysis FA 1 is an aqueous solution of a sodium salt containing two anions. (i) You will devise and perform a series of simple tests to identify the anions present in FA 1. Your tests should be based on the Qualitative Analysis Notes on pages 17 – 18 and should use only the bench reagents provided. Record your tests and observations in the space below. FA 1 does not contain SO32−, NO3− and NO2−. [4] (ii) Use your observations in (a)(i) to deduce the identity of the two anions in FA 1. anions: ………………………… and ……………………………… [2]

3 © Hwa Chong Institution 2025 9729/04/C2 Preliminary Examination DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN [Turn Over BLANK PAGE Question 1 continues on the next page.

4 © Hwa Chong Institution 2025 9729/04/C2 Preliminary Examination DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN (b) FA 2 is ZO2, an oxide of an unknown metal, Z. FA 3 is dilute sulfuric acid, H2SO4. FA 4 is a solid sample of potassium ethanedioate, K2C2O4. Perform the tests described in Table 1.1 and record your observations in the table. Test and identify any gases produced. Table 1.1 test observations (i) Transfer all of the solid sample of FA 4 into a boiling tube. Add all of FA 3 to this boiling tube. Gently warm the boiling tube. Turn off the Bunsen flame. Handle the hot boiling tube with care. Add FA 2 to the mixture in three separate portions using a spatula, shaking after each separate addition. Add all the remaining FA 2 to the mixture. Using the glass filter funnel , filter the mixture into a test tube and leave the filtrate to stand. Retain this filtrate for use in (b)(ii). [3] (ii) FA 5 is an aqueous solution of a cation of Z, which is also present in the filtrate from (b)(i). In this part, you are to investigate the effect of the addition of aqueous ammonia to separate portions of FA 5 and the filtrate from (b)(i). Table 1.2 test FA 5 filtrate from (b)(i) To 1 cm depth of FA 5 in a test tube, add aqueous ammonia dropwise, until in excess. Repeat using the filtrate from (b)(i). [3]

5 © Hwa Chong Institution 2025 9729/04/C2 Preliminary Examination DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN [Turn Over (iii) Identify the cation in FA 5. Explain with reference to your observations in Table 1.2. ion present is ……………………………………………………………………………………………. explanation ………………………………………………………………………………………………. ..………………………………………………………………………………………………………… [1] (iv) The filtrate from (b)(i) contains another cation of Z. Using your observations in Table 1.2, deduce the identity of th is ion and suggest how it was formed from test (b)(i). …………………………………………………………………………………………………………….. …………………………………………………………………………………………………………….. ………………………………………………………………………………………………………….. [1]

6 © Hwa Chong Institution 2025 9729/04/C2 Preliminary Examination DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN (c) FA 6 is an organic compound with a molecular formula of C4H8O2. It contains two functional groups. (i) Carry out the following tests. Carefully record your observations in Table 1.3. Unless otherwise stated, the volumes given below are approximate and should be estimated rather than measured. Table 1.3 test observations 1 Add 2 cm depth of aqueous silver nitrate to a clean boiling tube. Add 1 cm depth of aqueous sodium hydroxide slowly to the same boiling tube. Add aqueous ammonia slowly, with shaking, until the precipitate just dissolves. You may use a clean glass rod to help dissolve the precipitate. Add 2 cm depth of FA 6 to this mixture and shake the boiling tube. Place the boiling tube in the test-tube rack and leave it for 3 minutes. Important: After about 3 minutes, pour the mixture down the sink and wash out the boiling tube several times with tap water. 2 Add about 1 cm depth of FA 6 in a test-tube. To this test -tube, add 8 drops of sodium hydroxide solution followed by iodine solution, dropwise until no further change is seen. [3] (ii) State and explain the chemical change the reagent undergoes during the reaction in test 1. ………………………………………………………………………………………………………….… ……………………………………………………………………………………………………….…[1] (iii) Using your observations in Table 1.3, suggest the structure of FA 6. [1] [Total: 19]

7 © Hwa Chong Institution 2025 9729/04/C2 Preliminary Examination DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN [Turn Over 2 Determination of the order of reaction with respect to the concentration of iodine in the iodination of propanone FA 7 is 1.00 mol dm−3 propanone, CH3COCH3. FA 8 is an aqueous solution of iodine, I2. FA 9 is 1.00 mol dm−3 sulfuric acid, H2SO4. FA 10 is 0.50 mol dm−3 sodium hydrogencarbonate, NaHCO3. FA 11 is 0.0100 mol dm−3 sodium thiosulfate, Na2S2O3. Note: FA 9 is also used in Question 3. You are also provided with a starch indicator. The iodination of propanone, to form iodopropanone, proceeds as shown in the equation below. CH3COCH3(aq) + I2(aq) H+ → CH3COCH2I(aq) + HI(aq) reaction 1 This reaction is first order with respect to the concentration of CH3COCH3 and of H+ ions. You are to determine the order of reaction with respect to [ I2]. To do this, you will prepare a reaction mixture containing FA 7, FA 8 and FA 9. At different chosen times you will remove aliquots (fixed volumes) of this reaction mixture, add an excess of FA 10, and titrate the resulting solutions with FA 11. The titration reaction is given