YIJC 2021 Prelim P4_Answer

1 ãYIJC [Turn over YISHUN INNOVA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION CANDIDATE NAME CLASS DATE H2 CHEMISTRY 9729/04 Paper 4 Practical Paper Tuesday 24 August 2021 2 hours 30 minutes Candidates answer on question paper. No Additional Materials are required 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. For Examiner’s use 1 19 2 7 3 17 4 12 Total 55 Shift Laboratory

2 ãYIJC Answer all the questions in the spaces provided. 1 To determine the enthalpy change of neutralisation, ∆Hn The enthalpy change of neutralisation between an acid and an alkali can be determined using a type of experiment known as thermometric titration. One way of performing a thermometric titration involves using a fixed volume of alkali with progressive addition of small volumes of acid and monitoring the temperature of the reaction mixture during the process. You are to determine the enthalpy change of neutralisation for the reaction given below. HA(aq) + NaOH(aq) ® NaA(aq) + H2O(l) FA 1 is 1.80 mol dm–3 HA FA 2 is aqueous sodium hydroxide, NaOH In this experiment, you will measure the temperature of the contents of a polystyrene cup. You will analyse your results graphically in order to determine an accurate value for the temperature change of the mixture, caused by the neutralisation of aqueous HA and NaOH. You will use this value to calculate the heat change, q, for the experiment and hence determine a value for the enthalpy change of neutralisation for the reaction, ∆Hn. (a) Procedure 1. Place one polystyrene cup in a 250 cm3 beaker. 2. Rinse and fill the burette with FA 1. 3. Use a measuring cylinder to transfer 25 cm3 of FA 2 into the polystyrene cup. 4. Stir the solution in the cup with the thermometer. Read and record its temperature. 5. Run 5.00 cm3 of FA 1 into the cup. Stir the solution with the thermometer. Record the new temperature and volume of FA 1 added. 6. Run a second portion of 5.00 cm3 of FA 1 into the cup. Stir and record the new temperature and the total volume of FA 1 added. 7. Continue adding FA 1 in 5.00 cm3 portions. Stir and record each new temperature and the total volum