CJC 2026 Prelim P2 QP

[Turn over 9476/02 CJC JC2 Preliminary Examination 2026 CANDIDATE NAME CLASS 2T INDEX NUMBER CHEMISTRY 9476/02 Paper 2 Structured Questions 28 August 2026 2 hours You must answer on the Question Paper. You will need: Data Booklet INSTRUCTIONS • Answer all questions. • Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs. • Write your name, class and index number in the boxes at the top of the page. • Write your answer to each question in the space provided. • Do not use an erasable pen. Do not use correction fluid or tape. • You may use an approved calculator. INFORMATION • The total mark for this paper is 75. • The number of marks for each question paper or part question is shown in brackets [ ]. This document has 20 printed pages. For Examiner’s Use Paper 1 30 Paper 2 Q1 /16 Q2 / 8 Q3 /10 Q4 /18 Q5 /11 Q6 /12 75 Paper 3 75 Paper 4 50 OVERALL (100%) GRADE Catholic Junior College JC2 Preliminary Examination Higher 2

2 9476/02/CJC JC2 Preliminary Examination 2026 [Turn over Answer all questions in the spaces provided. 1 (a) Calcium fluoride, CaF2, is an ionic compound that occurs naturally in the mineral fluorspar. It is the major source of fluorine for the chemical industry including that of making fire retardants. Calcium fluoride can dissolve in water resulting in a decrease in temperature. (i) Name the force of attraction between particles in CaF2(s) and water molecules. …………………………………………………………………………………………..…[1] (ii) Fig. 1.1 shows the ions present in CaF2. Complete Fig. 1.1 to show: • the arrangement of two water molecules around one Ca2+(aq) ion • the arrangement of two water molecules around one F‒(aq) ion. Show clearly all the possible interactions between the ions and water molecules. Fig. 1.1 [1] (iii) Hence, suggest why the temperature decreases when CaF 2(s) dissolves in water. State and use the forces of attraction between the particles in CaF2(s) and between water molecules in your answer. …..……………………………………………………………………………...…………… …..……………………………………………………………………………...…………… ………………………………………………………………………………….…………… …………………………………………………………………………………………….… ……………………………………………………………………………………………[2]

3 9476/02/CJC JC2 Preliminary Examination 2026 [Turn over (b) The net effect of the individual processes that occur when CaF 2(s) dissolves in water produces an overall negative entropy change. (i) Explain what is meant by entropy. …………………………………………………………………………………………….… ……………………………………………………………………………………………[1] (ii) The processes that give positive entropy change include ions becom ing more mobile in the solution and an increase in number of particles. Describe one process, related to the arrangement of particles, that has a negative entropy change when CaF2(s) dissolves in water. …………………………………………………………………………………………….… …………………………………………………………………………………………….… ……………………………………………………………………………………………[1] (iii) The standard enthalpy change of solution of CaF2 is +46.0 kJ mol‒1 and the standard entropy change of solution is ‒44.9 J mol‒1 K‒1. Calculate the standard Gibbs free energy change of solution, G ꝋ , at 25 o C and state whether dissolving CaF2(s) in water is spontaneous. [2]

4 9476/02/CJC JC2 Preliminary Examination 2026 [Turn over (c) Enthalpy change of hydration of ions is not easily measured directly. By using Hess’ Law and the energy cycle, it can be obtained from experimental data. (i) Explain what is meant by enthalpy change of hydration. …………………………………………………………………………………………….… …………………………………………………………………………………………….… …………………………………………………………………………………………….… ……………………………………………………………………………………………[1] (ii) Table 1.1 gives data relevant to this question Table 1.1 process Ho / kJ mol‒1 standard lattice energy of CaF2(s) ‒2653 standard enthalpy change of solution of CaF2(s) +46.0 standard enthalpy change of hydration of calcium ions ‒1577 Use the data from Table 1.1 to calculate the standard enthalpy change of hydration of fluoride ions. [2] (iii) Suggest why the standard enthalpy change of hydration of chloride ions has a lower magnitude than that of fluoride ions. …………………………………………………………………………………………….… …………………………………………………………………………………………….… ……………………………………………………………………………………………[1]

5 9476/02/CJC JC2 Preliminary Examination 2026 [Turn over (d) Table 1. 2 shows the decomposition temperatures of two metal carbonates which are commonly used as flame retardants. Table 1.2 metal carbonate decomposition temperature / oC MgCO3 400 SrCO3 1340 (i) Write an equation for the thermal decomposition of MgCO3. …………………………………………………………………………………………..[1] (ii) Explain why the decomposition temperature of MgCO3 is lower than that of SrCO3. …..……………………………………………………………………………...…………… …..……………………………………………………………………………...…………… …..……………………………………………………………………………...…………… ………………………………………………………………………………….…………… …………………………………………………………………………………………….… ……………………………………………………………………………………………[3] [Total: 16]

6 9476/02/CJC JC2 Preliminary Examination 2026 [Turn over 2 Two vessels connected by a stopcock are filled respectively with two inert gases, gas A and gas B. The stopcock is then opened and the gases are allowed to mix at constant temperature of 80oC. gases pressure / kPa volume of vessel / cm3 boiling point / oC A 200 500 ─35.0 B 300 90 21.1 (a) (i) Calculate the final pressure in the connected vessel, assuming all gases behave ideally. [1] (ii) Predict qualitatively how the pressure calculated in (a)(i) will change when temperature drops from 80 oC to 30 oC. Explain your answer in terms of the change in kinetic energies of the gas molecules. …………………..………………………..………………………………………………….. …………………..………………………………………………………………………….... …………………..………………………………………………………………………….... …………………..…………………………………………………………………………... ……..………………………………………………………………………………………[2] (iii) The connected vessel is now cooled to 0 oC. Calculate the new pressure in the connected vessel. [2]

7 9476/02/CJC JC2 Preliminary Examination 2026 [Turn over (b) (i) Under what conditions of temperature and pressure would you expect a real gas to behave like an ideal gas? ……..………………………………………………………………………………………[1] (ii) The graph below shows the compressibility curve of 1 mole of hydrogen chloride gas. Draw the compressibility curve for 1 mole of steam in the graph below and explain the shape of your graph between low to moderate pressure. …………………..………………………………………………………………………….... …………….…….………………………………………………………………………….... …………………..………………………………………………………………………….... …………….…….………………………………………………………………………….... ……..………………………………………………………………………………………[2] [Total: 8] Pressure / Pa pV RT Ideal gas HCl 0

8 9476/02/CJC JC2 Preliminary Examination 2026 [Turn over 3 (a) The Corey House synthesis is an organic reaction that involves the reaction of a lithium dialkyl cuprate (R2CuLi) with an alkyl halide (R’X) to form a new alkane (R-R’), an organocopper compound and a lithium halide. The formation of propane from bromoethane using the Corey House reaction is shown below: (CH3)2CuLi + CH3CH2Br → CH3CH2CH3 + CH3Cu + LiBr (i) Draw the structural formulae of the three possible alkanes that could be formed with molecular formula C6H14, whe