2023 EJC H2 Chem Prelims P4 Solution

© EJC 9729/04/J2PE/23 [Turn Over EUNOIA JUNIOR COLLEGE JC2 Preliminary Examination 2023 General Certificate of Education Advanced Level Higher 2 CANDIDATE NAME CIVICS GROUP 2 2 – INDEX NUMBER CHEMISTRY Paper 4 Practical 9729/04 29 August 2023 2 hour 30 minutes Candidates answer on the Question Paper. Additional Materials: As listed in the Confidental Instructions

2 © EJC 9729/04/J2PE/23 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. Shift Laboratory Do not use paper clips, highlighters, glue or correction fluid. For Examiner’s Use 1 / 21 2 / 13 3 / 11 4 / 10 Total / 55 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. This document consists of 19 printed pages and 1 blank page. Answer all the questions in the spaces provided. 1 Determination of the kinetics of the reaction between thiosulfate ions an d acid FA 1 is aqueous sodium thiosulfate, Na2S2O3.

3 © EJC 9729/04/J2PE/23 [Turn Over FA 2 is 2.00 mol dm−3 dilute hydrochloric acid, HCl. Solid sulfur is one of the products formed in the reaction between sodium thiosulfate and hydrochloric acid, as shown in equation 1. The presence of sulfur causes the solution to become opaque. equation 1 S 2O2–3(aq) + 2H+(aq) ฀ SO2(g) + S(s) + H2O(l) In this experiment, the rate of this reaction is studied by measuring the time taken for the reaction mixture to become opaque. (a) Determination of order of reaction with respect to thiosulfate ions You will perform a series of five experiments. Then, you will graphically analyse your results in order to determine the order with respect to the concentrati on of thiosulfate ions, [S2O2–3]. For each experiment, you will note the volume of FA 1 added, VFA 1, and the time in seconds, t, taken for the reaction mixture to become opaque. In each experiment, you will need to ensure that the same total volume of reaction mixture is used by adding an appropriate volume of deionised water, Vwater, as required. You will then calculate values for ● 1000 t , to 1 decimal place ● 1000lg t    and  lg VFA 1 , to 3 significant figures Prepare a table in the space provided on page 4 in which to record, to an appropriate level of precision: ● all volumes, ● all values of t, ● all calculated values of 1000 t , 1000lg t    and  