YIJC 2025 Prelim P4 QP (for exchange)_H2 Chem

©YIJC 9729/04/JC2/PE/2025 [Turn over YISHUN INNOVA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CG INDEX NO CHEMISTRY Paper 4 Practical Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions 9729/04 25 August 2025 2 hours 30 minutes READ THESE INSTRUCTIONS FIRST Write your name and class in the spaces at the top of this page. 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. This document consists of 18 printed pages and 2 blank pages. Shift Laboratory For Examiner’s Use 1 / 16 2 / 17 3 / 6 4 / 16 Total / 55

2 ©YIJC 9729/04/JC2/PE/2025 Answer all the questions in the spaces provided. 1 Determination of concentrations of sodium hydroxide and of sodium carbonate in a mixture Sodium hydroxide reacts with hydrochloric acid according to the equation below: reaction 1 NaOH + HCl → NaCl + H2O Sodium carbonate reacts with hydrochloric acid in two separate stages. The reactions that occur are: reaction 2 Na2CO3 + HCl → NaCl + NaHCO3 reaction 3 NaHCO3 + HCl → NaCl + CO2 + H2O You are required to find the concentrations of sodium hydroxide and of sodium carbonate in FA 1 by means of a double-indicator titration. In a double-indicator titration, two different indicators are used, separately, in the same titration. For this experiment, you will be using thymolphthalein indicator followed by methyl orange indicator . Thymolphthalein indicates the end -point when reactions 1 and 2 are complete, while methyl orange indicates the end-point when reaction 3 is complete. FA 1 is a solution containing sodium hydroxide, NaOH, and sodium carbonate, Na2CO3. FA 2 is an aqueous solution containing 1.50 mol dm–3 hydrochloric acid, HCl. Solution T is thymolphthalein indicator. Solution M is methyl orange indicator. (a) Dilution of FA2 Use a burette to transfer 20.00 cm3 of FA 2 into a 250 cm3 volumetric flask. Make the solution up to the mark with deionised water and shake well to mix. Label this solution FA 3. This is a solution of hydrochloric acid of a concentration that is suitable for the titration. (b) (i) Titration of FA 1