RI 2024 Prelims P4 QP

© Raffles Institution 2024 9729/04/A/24 [Turn Over CANDIDATE NAME ( ) CLASS 24S0 RAFFLES INSTITUTION 2024 YEAR 6 PRELIMINARY EXAMINATION Higher 2 CHEMISTRY Paper 4 Practical 9729/04 21 August 2024 2 hours 30 minutes Do NOT turn over the Question Booklet until you are told to do so. READ THESE INSTRUCTIONS FIRST. Write your name and class on the space provided when instructed to do so. Give details of the practical shift and laboratory where appropriate, in the space provided. Write in dark blue or black pen. You may use a 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 number of marks is given in brackets [ ] at the end of each question or part question. 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 23 and 24. Shift Laboratory Bench Number For Examiner’s Use Question Marks 1 / 15 2 / 13 3 / 14 4 / 13 Total / 55 This document consists of 21 printed pages and 3 blank pages.

2 © Raffles Institution 2024 9729/04/A/24 [Turn Over Answer all the questions in the spaces provided. 1 Determination of the molar enthalpy change of solution, ∆Hsol, of FA 1 FA 1 is solid anhydrous magnesium sulfate, MgSO4. When added to water, FA 1 dissolves and the temperature of the solution rises. Some of the heat energy released from the dissolution of FA 1 is absorbed by the calorimeter. To determine the molar enthalpy change of solution, ∆Hsol, of FA 1, you will first need to determine the heat capacity of the calorimeter. The heat capacity of the calorimeter, Ccal, is the amount of heat energy required to change its temperature by 1 °C. The calorimeter used in this experiment comprises two polystyrene cups supported by a 250 cm3 glass beaker. (a) (i) Determination of the heat capacity of the calorimeter, Ccal When hot water is added to the calorimeter containing room temperature water, heat energy from the hot water is used to raise the temperature of the calorimeter and the room temperature water. To determine the heat capacity of the calorimeter, C cal, you will measure the maximum temperature rise when hot water is added to room temperature water in the calorimeter. You are to carry out the experiment and record all values of temperature, T, to an appropriate level of precision in Table 1.1. Procedure 1. Place a polystyrene cup inside a second polystyrene cup and place both cups in a 250 cm3 glass beaker. 2. Use a 50 cm3 measuring cylinder to transfer 50 cm3 of room temperature water into the polystyrene cup. 3. Carefully stir the water in the polystyrene cup with a thermometer. Read and record the temperature of the room temperature water, T1. Leave the thermometer in the polystyrene cup. 4. Use a 100 cm3 glass beaker to collect approximately 60 cm3 of hot water from the hot water dispenser. Note: Use a paper towel to hold the hot apparatus. Handle all hot apparatus with care. 5. Use the 50 cm 3 measuring cylinder to measure 50 cm 3 of hot water from the 100 cm3 glass beaker. Place another thermometer into the measuring cylinder. Read and record the temperature of the hot water, T2. Remove the thermometer from the hot water. 6. Immediately add the hot water from the measuring cylinder to the room temperature water in the polystyrene cup. Carefully stir the combined water using the thermometer and record the maximum temperature reached, T3. 7. Empty the polystyrene cup and dry it using the paper towel.

3 © Raffles Institution 2024 9729/04/A/24 [Turn Over Table 1.1 temperature of room temperature water, T1 / °C temperature of hot water, T2 / °C maximum temperature of combined water, T3 / °C (ii) Calculate the heat energy lost by the hot water and the heat energy gained by the room temperature water using the values you obtained in (a)(i). Assume that the specific heat capacity of water is 4.18 J g−1 K−1, and that the density of water is 1.00 g cm−3. heat energy lost by the hot water = ………………………..…… heat energy gained by the room temperature water = …………………………..… [2] (iii) The heat energy absorbed by the calorimeter during the experiment can be determined from the following equation. Heat energy absorbed by the calorimeter = heat energy lost by hot water – heat energy gained by room temp water Calculate the heat energy absorbed by the calorimeter and hence determine the heat capacity of the calorimeter, Ccal. Use the values you obtained from (a)(i) and (a)(ii). heat energy absorbed by the calorimeter = …………………………………… heat capacity of calorimeter, Ccal = …………………………………… [2]

4 © Raffles Institution 2024 9729/04/A/24 [Turn Over BLANK PAGE

5 © Raffles Institution 2024 9729/04/A/24 [Turn Over (b) (i) Determination of the molar enthalpy change of solution, ∆Hsol, of FA 1 In this experiment, you will measure the temperature of the water in a polystyrene cup at regular time intervals, before and after FA 1 is added. You will analyse your results graphically to obtain an accurate value for the temperature change caused by the dissolution of FA 1. You will use this value to calculate the total heat change, q, of the solution and the calorimeter, and hence determine the molar enthalpy change of solution, ∆Hsol, of FA 1. In the space provided on page 6 , prepare tables in which to record for your experiment: • all weighings to an appropriate level of precision • all values of temperature, T, to an appropriate level of precision • all values of time, t, recorded to 0.5 min. It is important that you measure each temperature at the specified time. Procedure 1. Weigh the capped container containing solid FA 1. Record the mass in your table on page 6. 2. Place a polystyrene cup inside a second polystyrene cup and place both cups in a 250 cm3 glass beaker. 3. Use a measuring cylinder to transfer 100 cm 3 of room temperature water into the polystyrene cup. 4. Carefully stir the water in the polystyrene cup with the thermometer. Read and record the temperature, T. Start the stopwatch (t = 0.0 min). The stopwatch must be left to run for the rest of the experiment. 5. Continue to stir the water in the polystyrene cup. Read and record T every 0.5 minute for two minutes. 6. At exactly 2.5 minutes, transfer all the solid FA 1 to the polystyrene cup. Stir the solution but do not read T. 7. Continue to stir the solution. Read and record T at t = 3.0 min and every 0.5 min until t = 8.0 min. 8. Reweigh the empty capped container. Record this mass in your table on page 6.

6 © Raffles Institution 2024 9729/04/A/24 [Turn Over Results [3]

7 © Raffles Institution 2024 9729/04/A/24 [Turn Over (ii) Plot a graph of temperature, T, on the y-axis against time, t, on the x-axis, on the grid in Fig. 1.1. Draw a best-fit straight line taking into account all of the points before t = 2.5 min.