Copy of KCPSS_2024_4E_Chem_Prelim_P3

] KUO CHUAN PRESBYTERIAN SECONDARY SCHOOL 2024 Preliminary Examination Secondary 4 Express NAME CLASS REG. NO CHEMISTRY 6092/03 Paper 3 Practical 14 August 2024 1 hour 50 minutes Candidates answer on the Question Paper. Setter : Mr. Sam Yew Yishen READ THESE INSTRUCTIONS FIRST Write your name, class and register number on all the work you hand in. Write in dark blue or black pen. You may use a soft 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 page 14. 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 17 2 10 3 13 Total 40 This document consists of 13 printed pages and 1 blank page.

2 KCPSS 2024/Sec 4Exp Prelim Chemistry P3 1 Malic acid is a carboxylic acid found in apple juice. The equation for the reaction between malic acid, H 2C4H4O5, and aqueous potassium hydroxide, KOH, is shown. 2KOH + H2C4H4O5  K2C4H4O5 + 2H2O Read all instructions below carefully before starting the experiment in Question 1. Instructions The concentration of aqueous malic acid is determined by titration with aqueous potassium hydroxide, KOH. Thymolphthalein indicator, is used to determine the end-point of the titration. P is apple juice containing malic acid. Q is 0.0500 mol/dm 3 aqueous potassium hydroxide, KOH(aq). I is thymolphthalein indicator. (a) (i) Fill the burette with P. Use the pipette to transfer 25.0 cm 3 of Q into a conical flask. Add a few drops of thymolphthalein indicator, I, to the solution in the conical flask. Ensure the lid is placed back on the vial of I after use. Add P from the burette, swirling the flask constantly. At the end-point, one drop of P would cause the solution to remain colourless for at least 30 seconds. The end-point is when the solution remains colourless for 30 seconds. Record your titration results in the space provided. Repeat the titration as many times as you consider necessary to achieve consistent results. Results [5]

3 KCPSS 2024/Sec 4Exp Prelim Chemistry P3 (ii) From your titration results, obtain an average volume of P to be used in your calculations. Show clearly how you obtained this volume.