EJC 2024 JC2 Prelim P4 Solutions

© EJC 9729/04/J2Prelim/24 [Turn Over EUNOIA JUNIOR COLLEGE JC2 Preliminary Examination 2024 General Certificate of Education Advanced Level Higher 2 CANDIDATE NAME CIVICS GROUP 2 3 – INDEX NUMBER CHEMISTRY Paper 4 Practical 9729/04 15 August 2024 2 hour 30 minutes Candidates answer on the Question Paper. Additional Materials: As listed in the Confidental Instructions READ THESE INSTRUCTIONS FIRST Write your name, civics group and registration number on 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 paper clips, highlighters, glue or correction fluid. 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. 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 / 9 2 / 11 3 / 22 4 / 13 Total / 55 This document consists of 19 printed pages and 1 blank page.

2 © EJC 9729/04/J2Prelim/24 For Examiner’s Use Answer all the questions in the spaces provided. 1 Investigation of some reactions of ascorbic acid Ascorbic acid, more commonly known as vitamin C, is a water-soluble vitamin with molecular formula, C 6H8O6. Ascorbic acid is a well -known antioxidant that is reasonably stable in the solid form but oxidised quite rapidly by oxygen in air once dissolved in water. FA 1 is a solution of ascorbic acid, C6H8O6. FA 2 is a solution of copper(II) sulfate, CuSO4 FA 6 is 1.0 mol dm–3 hydrochloric acid, HCl Carry out the following test. 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. Table 1.1 test observations (a) Add 2 cm depth of aqueous silver nitrate to a clean dry boiling tube. Add 1 cm depth of aqueous sodium hydroxide slowly to the same tube. Brown ppt formed. Add aqueous ammonia slowly, with shaking until the precipitate just dissolves. You may use a clean glass rod to help dissolve the precipitate. Colourless solution obtained. Add 1 cm depth of FA 1 to this mixture and shake the tube. Place the boiling tube in the test -tube rack and leave it for 3 minutes. Grey ppt formed. [1] Silver mirror formed on side of boiling tube/Grey ppt remains /no further change [1] Important: After about 3 minutes, pour the mixture down the sink and wash out the boiling tube several times with tap water. [2]

3 © EJC 9729/04/J2Prelim/24 [Turn Over For Examiner’s Use Table 1.2 test ob