2026 RI H2 Chem Prelims P2 Questions

© Raffles Institution 2026 9476/02/S/26 RAFFLES INSTITUTION 2026 YEAR 6 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY 9476/02 Paper 2 Structured Questions 15 September 2026 2 hours You must answer on the Question Paper. You will need: Data Booklet INSTRUCTIONS Do not open this question booklet until you are told to do so. • 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 spaces at the top of this page. • Write your answer to each of the question in the space provided. • Do not use an erasable pen. Do not use correction tape or fluid. • You may use an approved calculator. • A Data Booklet is provided. Do not write anything in it. INFORMATION • The total mark for this paper is 75. • The number of marks for each question or part question is shown in brackets [ ]. For Examiner’s Use 1 / 13 2 / 15 3 / 16 4 / 16 5 / 15 Total / 75 This document has 24 pages. Any blank pages are indicated.

2 © Raffles Institution 2026 9476/02/S/26 Answer all questions in the space provided. 1 (a) In terms of structure and bonding, explain the variation of melting points between Na2O, SiO2 and SO3. ……………………………………………………………………………………..………………….. ……………………………………………………………………………………..………………….. ……………………………………………………………………………………..………………….. ……………………………………………………………………………………..………………….. ……………………………………………………………………………………..………………….. ……………………………………………………………………………………..………………….. ……………………………………………………………………………………..………………….. ……………………………………………………………………………………..………………….. ……………………………………………………………………………………..………………….. …………………………………………………………………………………………………….. [4] (b) Table 1.1 shows the melting points of MgO and Al2O3. Table 1.1 compound melting point / °C MgO 2830 Al2O3 2054 Explain the difference in the melting points of MgO and Al2O3. …………………………………………………………………………………… ..….............. …………………………………………………………………………………… ..….............. …………………………………………………………………………………… ..….............. …………………………………………………………………………………… ..….............. ……………………………………………………………………………………..….................. [2]

© Raffles Institution 2026 9476/02/S/26 [Turn Over 3 (c) Al2O3 is produced commercially from bauxite ore via the Bayer process. Bauxite consists mainly hydrated Al2O3, with Fe2O3 as an impurity. Impure Al2O3 is first treated with NaOH(aq) at an elevated temperature, where Fe2O3 does not react with NaOH(aq). (i) Write an equation for this step. ……………………………………………………………………………………..…......... [1] (ii) Suggest how Fe2O3 is removed in this step. ……………………………………………………………………………………..…......... [1] The second step involves cooling the resultant solution, which results in the precipitation of Al(OH)3. The final step involves the thermal decomposition of A l(OH)3 to form A l2O3 carried out at 1000 oC, in a reaction vessel of fixed volume. 2Al(OH)3(s) ⇌ Al2O3(s) + 3H2O(g) H > 0 Table 1.2 shows the percentage yield of Al2O3(s) under different pressures. Table 1.2 pressure / atm % yield 1.0 82.0 5.0 60.0 10.0 45.0 (iii) Suggest a cost-effective way of increasing the yield of Al2O3 in this final step of the Bayer process. ……………………………………………………………………………………..…............. ……………………………………………………………………………………..…......... [1]

4 © Raffles Institution 2026 9476/02/S/26 Table 1.3 shows some thermodynamic data for the decomposition of Al(OH)3. Table 1.3 Temperature / oC ∆Gr kJ mol−1 1000 − 422.17 1500 − 660.78 (iv) State the equation that relates ∆Gr to ∆Hr and ∆Sr. ……………………………………………………………………………………..…......... [1] (v) Use Table 1.3 to calculate ∆Sr in J K-1 mol−1. [2] (vi) Suggest how the ∆Sr might change if the temperature was below 100 oC. ……………………………………………………………………………………..…............. ……………………………………………………………………………………..…............. ……………………………………………………………………………………..…......... [1] [Total: 13]

© Raffles Institution 2026 9476/02/S/26 [Turn Over 5 2 (a) State two basic assumptions of kinetic theory as applied to an ideal gas. …………………………………………………………………………………… ..….............. …………………………………………………………………………………… ..….............. ……………………………………………………………………………………..….................. [2] Ethanol, hydrogen, octane and pentane are examples of fuels used in automobiles. Table 2.1 shows some properties of ethanol, pentane and octane. Table 2.1 compound boiling point / C Mr ∆Hc / kJ mol−1 ethanol 78 46.0 −1367 pentane 36 72.0 −3509 octane 125 114.0 −5471 (b) (i) State the general gas equation. ……………………………………………………………………………………..…......... [1] (ii) Hence, calculate the volume occupied by 5.0 g of gaseous octane at 250 C and 1.0 atm. [1] (iii) Use data from Table 2.1 to arrange the three gases in order of increasing relative deviation from ideal gas behaviour at moderately high pressure. Explain your answer. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..…......... [2]

6 © Raffles Institution 2026 9476/02/S/26 (c) Hydrogen is mainly produced by the steam-methane reforming reaction in the industry. H2O(g) + CH4(g) ⇌ CO(g) + 3H2(g) ∆H = +193 kJ mol−1 (i) Explain what is meant by dynamic equilibrium. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..…......... [1] (ii) Equimolar amounts of steam and methane are added to a sealed vessel and heated to 1000 K. At equilibrium, 40.7% of the methane has reacted. The total pressure in the vessel is 10.0 atm at equilibrium. Calculate the value of Kp for this reaction, giving its units. [3]

© Raffles Institution 2026 9476/02/S/26 [Turn Over 7 (iii) In another steam-methane equilibrium mixture, the volume of the container is halved at constant temperature. Explain how the partial pressure of methane changes with time until the system reaches a new equilibrium. ……………………………………………………………………………………..….............. ……………………………………………………………………………………..….............. …………………………………………………………………………………… ..…...... [2] (iv) At time = t0, another steam-methane mixture is at equilibrium. The temperature of this mixture is decreased instant aneously at constant volume at time = t 1 and a new equilibrium is established at time = t2. Complete Figure 2.1 below to show how the forward rate changes from t0 onwards. Figure 2.1 [3] [Total: 15] t0 t1 time / s forward rate / mol dm−3 s−1 t2

8 © Raffles Institution 2026 9476/02/S/26 3 Polar functional groups in organic compounds that contain an electron-deficient carbon atom are prone to reacting with nucleophiles. (a) The compounds in Table 3.1 react with KCN. Complete Table 3.1 by stating the reagents and conditions required and identifying the type of reaction which occurs. Table 3.1 compound reagents and conditions required for reaction type of reaction CH3CH2Cl (CH3)2CO [2] (b) The pKa data for some common compounds are given in Table 3.2. Table 3.2 compound pKa conjugate base HBr –9 Br – CH3COOH 4.8 CH3COO– H2O 15.7 OH– CH3CH2OH 16 CH3CH2O– CH4 50 CH3– (i) State the relationship between the p Ka of the compounds and the stability of their conjugate bases.