2020 JPJC Prelim Paper 4 QP

 Jurong Pioneer Junior College [Turn Over NAME CLASS 19S JURONG PIONEER JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION 2020 CHEMISTRY 9729/04 Higher 2 Paper 4 Practical 2 September 2020 2 hours 30 minutes Candidates answer on the Question paper. Additional Materials: As listed in the Confidential Instructions READ THESE INSTRUCTIONS FIRST Write your name, class and exam 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, graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. Do not spend more than 40 minutes on Q1 and Q2. 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 18 and 19. Shift At the end of the examination, fasten all your work securely together. Laboratory The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 /8 2 /9 3 /22 4 /16 Total /55 This document consists of 19 printed pages.

2  Jurong Pioneer Junior College 9729/04/J2 PRELIMINARY EXAM/2020 Answer all the questions in the spaces provided. 1 Inorganic Qualitative Analysis FA 1 is a solid sample which contains two cations and one anion. One of the cations is Fe3+. Perform the tests described in Table 1.1 and record your observations in the table. Test and identify any gases evolved. If there is no observable change, write no observable change. For Examiner’s Use Table 1.1 tests observations (a) (i) Add one spatula full of FA 1 into a test-tube. Place about 5 cm depth of deionised water into the test -tube and shake the mixture until all the solid has dissolved. Use this FA 1 solution for tests (ii) and (iii). (ii) To a 2 cm depth of FA 1 solution in a test-tube, add one spatula of solid sodium carbonate. (iii) To a 1 cm depth of FA 1 solution in a boiling tube , add aqueous sodium hydroxide dropwise, with shaking, until it is in excess. Gently warm the mixture. Then filter the mixture, collecting the filtrate in a clean test-tube. Keep the filtrate for test (iv). (iv) To a 1 cm depth of the filtrate from test (iii) in a test tube, add BaCl2(aq) dropwise. Then add dilute hydrochloric acid until no further change. [5]

3  Jurong Pioneer Junior College 9729/04/J2 PRELIMINARY EXAM/2020 [Turn Over (b) (i) By considering the observations made in Table 1.1 and making reference to the Qualitative Analysis Notes, identify the other cation and the anion present in FA 1. For Examiner’s Use The other cation in FA 1 is ……………………….. The anion in FA 1 is ……………………….. [2] (ii) By considering the i ons present in FA 1 , suggests an explanation for observations made in test (a)(ii). ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [1] [Total: 8]

4  Jurong Pioneer Junior College 9729/04/J2 PRELIMINARY EXAM/2020 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 C4H8O2. 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. Do not use Bunsen burner for heating. Use the hot water provided. For Examiner’s Use 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. (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. (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 10 drops of aqueous sodium hydroxide. Now add iodine solution dropwise, until a permanent yellow/ orange colour is obtained. Warm the mixture in the water bath for two minutes. (iv) Place about 1 cm depth of FA 2 in a test-tube. To this test -tube, cautiously add a small piece of sodium metal. Effervescence observed. H2 gas produced extinguishes a lighted splint with a “pop” sound. (v) Place about 1 cm depth of FA 2 in a test-tube. To this test-tube, add 2,4-dinitrophenylhydrazine dropwise. Orange ppt. formed [3]

5  Jurong Pioneer Junior College 9729/04/J2 PRELIMINARY EXAM/2020 [Turn Over (b) (i) Using the observations in (a)(ii) and (v) in Table 2.1, identify one functional group present in FA 2. Give evidence(s) to support your conclusion. For Examiner’s Use Functional group: …………………………………………………………… Evidence: …………………………………………………………………… ………………………………………………………………………………. [2] (ii) Using the observations in other tests in Table 2.1, identify the other functional group present in FA 2. Give evidence(s) to support your conclusion. Functional group: …………………………………………………………… Evidence: …………………………………………………………………… ………………………………………………………………………………. [2] (iii) Suggest two possible structures of FA 2. [2] [Total: 9]

6  Jurong Pioneer Junior College 9729/04/J2 PRELIMINARY EXAM/2020 3 Investigation of reaction between manganate(VII) ions and ethanedioate ions. For Examiner’s Use FA 3 is 0.0100 mol dm–3 sodium thiosulfate, Na2S2O3 FA 4 is 0.0200 mol dm–3 potassium manganate(VII), KMnO4 FA 5 is 0.200 mol dm–3 ethanedioic acid, H2C2O4 FA 6 is 1.0 mol dm–3 sulfuric acid, H2SO4 FA 7 is 0.100 mol dm–3 potassium iodide, KI You are also provided with a starch indicator. Acidified potassium manganate(V II) oxidises ethanedioate ions, C 2O42 as shown in reaction 1 . The Mn 2+ ions produced in reaction 1 act as a catalyst for the reaction . This is an example of ‘autocatalysis’. 2MnO4–(aq) + 5C2O42(aq) + 16H+(aq)  2Mn2+(aq) + 10CO2(g) + 8H2O(l) reaction 1 You are to investigate how the rate of reaction changes with [MnO 4]. To do this, you will prepare a reaction mixture containing FA 4, FA 5 and FA 6. At timed intervals, you will withdraw five aliquots (portions) of the reaction mixture, add them to 10 cm 3 of excess KI which will “quench” the reaction by reacting away all MnO 4 via a redox reaction as shown in reaction 2. 2MnO4–(aq) + 10I(aq) + 16H+(aq)  2Mn2+(aq) + 5I2(aq) + 8H2O(l) reaction 2 You will then titrate the iodine produced in the resulting solutions against sodium thiosulfate (reaction 3). 2S2O32(aq) + I2(aq)  2I(aq) + S4O62(aq) reaction 3 Your titre values will indicate the concentration of MnO4 remaining in the reaction mixture at different times. Hence, the rate of reaction between MnO 4 and C2O42 at different times can be determined by graphical analysis of your results. You should read all of the instructions on this page and the Method on the next page before you start this experiment. Recording your results In an appropriate format in the space provided on page 8, prepare a table to record, for each of your aliquots, the  transfer time in minutes and seconds  titration resul