NYJC 2023 H2 Chemistry 9729 P4

[Turn Over NANYANG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME TUTOR’S NAME CLASS CHEMISTRY 9729/04 Paper 4 Practical 16 August 2023 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 and class 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, 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. Shift Laboratory For Examiner’s Use 1 / 14 2 / 18 3 / 10 4 / 13 Total / 55 This document consists of 20 printed pages

2 H2 Chemistry 9729/04 NYJC J2/2023 PRELIM 1 Investigation of the reaction between phosphoric acid and sodium hydroxide FA 1 is an aqueous solution of phosphoric acid, H3PO4. FA 2 is 0.115 mol dm–3 sodium hydroxide, NaOH. In this experiment you are to investigate the reaction between phosphoric acid and sodium hydroxide in order to determine the chemical equation. Solution I is thymolphthalein indicator. (a) (i) Procedure Dilution of FA 1 1. Use the pipette to transfer 10.0 cm 3 of FA 1 into a 250 cm3 volumetric flask. 2. Make the solution up to the mark with deionised water and shake well to mix. 3. Label this solution FA 3. Titration of FA 3 against FA 2 4. Fill the burette with FA 2. 5. Use the pipette to transfer 25.0 cm 3 of FA 3 into a 250 cm3 conical flask. 6. Add a few drops of solution I to the conical flask. 7. Run FA 2 from the burette into the conical flask. The end-point is reached when the solution changes from colourless to a permanent pale blue colour. 8. Record your titration results, to an appropriate level of precision, in the space provided below. 9. Repeat points 5 to 8 until consistent results are obtained. Results [4]

3 H2 Chemistry 9729/04 NYJC J2/2023 PRELIM [Turn Over (ii) From your titrations, obtain a suitable volume of FA 2 to be used in your calculations. Show clearly how you obtained this volume. volume of FA 2 = cm3 [1] (b) (i) Calculate the amount of sodium hydroxide present in the volume of FA 2 calculated in (a)(ii). amount o