2025 RI H2Chem Prelims P4 Questions

1 © Raffles Institution 2025 9729/04/A/25 [Turn Over CANDIDATE NAME ( ) CLASS 25S0 RAFFLES INSTITUTION 2025 YEAR 6 PRELIMINARY EXAMINATION Higher 2 CHEMISTRY Paper 4 Practical 9729/04 27 August 2025 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 / 14 2 / 19 3 / 13 4 / 9 Total / 55 This document consists of 21 printed pages and 3 blank pages.

2 © Raffles Institution 2025 9729/04/A/25 [Turn Over Answer all the questions in the spaces provided. 1 Investigation of inorganic and organic compounds (a) FA 1 is an aqueous solution containing two cations. FA 2 is an aqueous solution containing one anion. You will perform tests to identify • the two cations present in FA 1 • the anion present in FA 2. (i) Carry out the following tests. Carefully record your observations in Table 1.1. The volumes given below are approximate and should be estimated rather than measured. Test and identify any gases evolved. If there is no observable change, write no observable change. Table 1.1 tests observations 1 Test FA 1 with Universal Indicator paper. 2 Add 1 cm depth of FA 1 into a test-tube. Add aqueous sodium hydroxide, slowly with shaking, until no further change is seen. Filter the mixture into a clean test-tube. To the filtrate, add dilute nitric acid drop-wise until in excess. 3 Add 1 cm depth of FA 2 into a test-tube. Add 1 cm depth of dilute nitric acid. [5]

3 © Raffles Institution 2025 9729/04/A/25 [Turn Over (ii) Use your observations in Table 1.1 to identify the two cations in FA 1 and the anion in FA 2 and state the evidence of each by completing Table 1.2. Table 1.2 identity evidence cation in FA 1 cation in FA 1 anion in FA 2 [3]

4 © Raffles Institution 2025 9729/04/A/25 [Turn Over (b) FA 3 and FA 4 are aqueous solutions of two organic compounds Y and Z respectively. Both Y and Z contain only two carbon atoms. You will perform some of the tests described in Table 1.3. You will then deduce the identities of Y and Z present in FA 3 and FA 4 respectively. In addition to having access to the usual bench reagents, you are also provided with the following: • magnesium turnings • iodine solution Perform the tests described in Table 1.3. Some of the observations have been completed for you. There is no need to carry out these tests. Record your observations in Table 1.3. Test and identify any gases evolved. If there is no observable change, write no observable change. Table 1.3 tests observations with FA 3 observations with FA 4 (i) Add 1 cm depth of FA 3 to a test-tube. Add all of the magnesium turnings provided in the vial to this test-tube. no observable change (ii) Add about 1 cm depth of FA solution to a test -tube. To this test-tube, add 8 drops of sodium hydroxide solution followed by iodine solution, dropwise, until a permanent orange/red colour is present. (iii) Add 1 cm depth of aqueous silver nitrate to a test -tube. Then slowly add 1 cm depth of aqueous sodium hydroxide. Add aqueous ammonia slowly, with shaking, until the precipitate just dissolves. You may use a clean glass rod to stir the mixture and help dissolve the precipitate. Add 1 cm depth of FA 4 to this mixture, shake the tube and place it in the test-tube rack to stand. no observable change [4]

5 © Raffles Institution 2025 9729/04/A/25 [Turn Over (iv) Using your observations in Table 1.3, complete Table 1.4 with the identities of Y and Z in FA 3 and FA 4 respectively. Table 1.4 identity Y in FA 3 Z in FA 4 [2] [Total: 14]

6 © Raffles Institution 2025 9729/04/A/25 [Turn Over BLANK PAGE

7 © Raffles Institution 2025 9729/04/A/25 [Turn Over 2 Determination of enthalpy change of reaction for some acid-base reactions FA 5 is 0.60 mol dm−3 sodium hydrogencarbonate, NaHCO3. FA 6 is aqueous sodium hydroxide, NaOH, of unknown concentration. This experiment involves two different acid-base reactions. The reaction between sodium hydrogencarbonate, FA 5, and sodi um hydroxide, FA 6 is shown. reaction 1 NaHCO3(aq) + NaOH(aq) ⎯→ Na2CO3(aq) + H2O(l) H1 The molar enthalpy change for reaction 1, H1, is the enthalpy change when 1.00 mol of NaHCO3 reacts completely with NaOH. In this experiment, you will perform a thermometric titration to determine the equivalence point for the reaction of FA 5 and FA 6, where maximum heat is evolved, without the use of an indicator. You will follow the reaction by measuring the temperature as volumes of FA 6 are added in regular portions from a burette to a fixed volume of FA 5 placed in a polystyrene cup. The data obtained will allow you to determine the temperature change. Then, you will analyse your results graphically in order to determine the equivalence point of the reaction. (a) Determination of the enthalpy change of reaction between FA 5 and FA 6 Prepare a table in the space provide d on page 8 and record, to the appropriate level of precision: • all volumes of FA 6 added, VFA 6 • total volume of solution in the cup, Vtotal • the maximum temperature, T, reached after each addition of base, FA 6. It is important that the volume of FA 6 recorded is the total volume you have added up to the point when the temperature reading was made. Note: If you overshoot on an addition, record the actual total volume of FA 6 added up to that point. In the same table, you also need to calculate the corresponding values of: • T = T – T0, where T0 is the initial temperature of FA 5 • (Vtotal × T) to 3 significant figures.

8 © Raffles Institution 2025 9729/04/A/25 [Turn Over Procedure 1. Fill the burette labelled FA 6 to the 0.00 cm3 mark with FA 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 40.0 cm3 of FA 5 into the first cup. 4. Measure and record the initial temperature of FA 5, T0. 5. Run 5.00 cm3 of FA 6 from the burette into the cup and stir the solution gently with the thermometer. Record both the maximum temperature and the actual total volume of FA 6 added. 6. Immediately run a further 5.00 cm3