2021 ACJC H2 Chem Prelim P4 Ans_for sharing with other schools

Name Index Number Form Class Tutorial Class Subject Tutor ANGLO-CHINESE JUNIOR COLLEGE DEPARTMENT OF CHEMISTRY Preliminary Examination CHEMISTRY 9729/04 Higher 2 Paper 4 Practical 3 August 2021 2 hours 30 minutes Candidates answer on the Question Paper. READ THESE INSTRUCTIONS CAREFULLY Write your name, class 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. 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 19 and 20. 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. For Examiner’s Use Question No. Marks 1 (15 m) 2 (23 m) 3 (17 m) Presentation of answers TOTAL (55 m) This document consists of 19 printed pages and 1 blank page. 9729/04/Prelim/2021 ANGLO-CHINESE JUNIOR COLLEGE © ACJC 2021 Department of Chemistry [Turn over Shift Laboratory

© ACJC 2021 9729/04/Prelim/2021 [Turn over 2 1 Determination of the total concentration of ethanedioate ions with sodium hydroxide and potassium manganate(VII) (a) Procedure FA 1 is an aqueous mixture of ethanedioic acid, H 2C2O4, and sodium ethanedioate, Na2C2O4 FA 2 is 0.100 mol dm–3 sodium hydroxide, NaOH FA 3 is 0.0200 mol dm–3 potassium manganate(VII), KMnO4 You are advised to read parts (a)(i) and (a)(ii) before starting practical work and to carry out a ROUGH titration until the relevant colour change is seen in each part of the titration. (i) Determine by titration, with sodium hydroxide, the concentration, in mol dm–3, of the ethanedioic acid in FA 1.  Fill the burette with FA 2.  Pipette 25.0 cm3 of FA 1 into a conical flask and add to the flask a few drops of thymol blue indicator.  Run FA 2 from the burette into the conical flask until the solution turns green (just before it turns blue).  Repeat the titration as many times as necessary to provide reliable results.  Tabulate your titration results in the space provided. (ii) Determine by titration, with potassium manganate( VII), the total concentration, in mol dm–3, of ethanedioate ions in FA 1.  Fill the second burette with FA 3.  Pipette 25.0 cm 3 of FA 1 into a conical flask. Use the measuring cylinder provided to add to the flask 25 cm 3 of 1 mol dm –3 sulfuric acid, 10 cm 3 of 0.