HCI 2022 H2 Chemistry Prelim P4 QP and Ans

HWA CHONG INSTITUTION C2 Preliminary Examination Higher 2 NAME CT GROUP 21S CHEMISTRY Paper 4 Practical Candidates answer on the Question Paper 9729/04 25 August 2022 2 hours 30 minutes 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 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 16 and 17. 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 2 3 4 Total This document consists of 17 printed pages.

2 © Hwa Chong Institution 2022 9729/04/C2Prelim 2022 [Turn over 1 Determination of the basicity of an acid and the strength of a base FA 1 is 1.50 mol dm–3 sodium hydroxide, NaOH. FA 2 is 0.75 mol dm–3 acid A, which is either monobasic (monoprotic) or dibasic (diprotic). FA 3 is 1.50 mol dm–3 base B, which is monoacidic (monoprotic) and is either a strong base or a weak base. You will perform experiments to determine whether acid A is monobasic or dibasic. You will then calculate the enthalpy change of neutralisation, Hneut, between NaOH and acid A. You will also design one more experiment to determine whether base B is a strong base or a weak base. (a) (i) Experiment 1 1. Place one polystyrene cup inside a second polystyrene cup. Place these in a glass beaker to prevent them from tipping over. 2. Use a measuring cylinder to transfer 40.0 cm3 of FA 1 into the first polystyrene cup. Stir the FA 1 in the polystyrene cup with the thermometer with 0.2 °C divisions. Read and record the initial temperature of FA 1 in Table 1.1. 3. Use another measuring cylinder to measure 20.0 cm3 of FA 2. Add FA 2 to FA 1 in the polystyrene cup. Stir the mixture using the same thermometer and record the maximum temperature reached. 4. Wash and dry the thermometer and the polystyrene cup. Experiment 2 Repeat experiment 1 using 20.0 cm3 of FA 1 and 40.0 cm3 of FA 2. Use your results to determine the maximum change in temperature , T, for each experiment and complete Table 1.1. You may assume that the initial temperature of FA 2 is the same as that of FA 1. Table 1.1 experiment Volume of FA 1 /cm3 Volume of FA 2 /cm3 Initial temperature of FA 1 /C Maximum temperature /C Maximum change in temperature, T /C 1 40.0 20.0 29.8 32.9 3.1 2 20.0 40.0 29.8 36.0