ASRJC 2026 Prelim P2 QP

ASRJC JC2 PRELIM 2026 9476/02/H2 [Turn over ANDERSON SERANGOON JUNIOR COLLEGE 2026 JC 2 PRELIMINARY EXAMINATION NAME:______________________________ ( ) CLASS: 26 / _____ CHEMISTRY 9476/02 Paper 2 Structured Questions 26 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 a pencil for any diagrams or graphs. • Write your name, class and register number on the blanks at the top of the page. • Write your student ID on the right. Using a dark pencil, completely shade the corresponding circles for the digit or letter in each column. Cleanly erase any mistakes. • 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 or part question is shown in brackets [ ]. For Examiner’s Use Paper 2 1 /12 2 /11 3 /13 4 /21 5 /18 Total /75 This document has 24 printed pages. Any blank pages are indicated.

2 ASRJC JC2 PRELIM 2026 9476/02/H2 Do not write in margin Answer all the questions in the spaces provided. 1 Chromium, Cr, and its compounds are widely used in many chemical reactions. (a) Cr exists as four stable isotopes. (i) Describe, in terms of the number of particles, how an atom of 54Cr differs from an atom of 52Cr. ……………………………………………………………………………………………… ……………………………………………………………………………………………[1] (ii) Write an equation to represent the first ionisation energy of chromium. ……………………………………………………………………………………………[1] (iii) Suggest how the value for the first ionisation energy of 54Cr compares with the first ionisation energy of 52Cr. Explain your answer in terms of the factors that affect ionisation energy. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………[3] (b) (i) Complete the following electronic configuration of chromium. 1s2 ……………………………………………………………………………………….[1] (ii) Deduce the total number of unpaired electrons in an atom of chromium. ……………………………………………………………………………………………[1]

3 ASRJC JC2 PRELIM 2026 9476/02/H2 [Turn over Do not write in margin (c) In an acidic solution, a dynamic equilibrium is established between CrO 42−(aq) and Cr2O72−(aq). 2CrO42−(aq) + 2H+(aq) Cr2O72−(aq) + H2O(l) (i) Explain what is meant by the term dynamic equilibrium. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………[1] (ii) CrO42−(aq) ions are yellow and Cr2O72−(aq) ions are orange. State what is observed when water is added to an orange solution containing an equilibrium mixture of acidified CrO42−(aq) ions and Cr2O72−(aq) ions. Explain your answer. observation: ………………………………………………………………………………. explanation: ………………………………………………………………………………. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………[2] (d) Chromium(IV) fluoride, CrF 4, is a covalent molecule that shows similar chemical properties to SiCl4. (i) Write an equation for the hydrolysis of CrF4 in water. …………………………………………………………………………………………...[1] (ii) Explain why CrF4 can hydrolyse in water. ……………………………………………………………………………………………… ……………………………………………………………………………………………… …………………………………………………………………………………….……..[1] [Total: 12]

4 ASRJC JC2 PRELIM 2026 9476/02/H2 Do not write in margin 2 (a) Fig. 2.1 shows how the entropy, S, of pure iron changes with temperature, T. T1 and T2 represent the melting point and boiling point of iron respectively. Fig. 2.1 (i) Explain what is meant by entropy. ……………………………………………………………………………………………… …..……………………………………………………………………………………….[1] (ii) Complete Fig. 2.1 above by drawing suitable graph line(s) to show the effect of increasing temperature on the entropy of iron: • at T2, and • from T2 to T3 [1] (iii) With reference to the entropy change observed at T1, explain your answer in (a)(ii) for the entropy change you have expected at T2. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………[1]

5 ASRJC JC2 PRELIM 2026 9476/02/H2 [Turn over Do not write in margin (b) Iron is extracted from iron(III) oxide (Fe2O3) primarily through smelting in a blast furnace. Reaction I shows the reduction of Fe2O3 by carbon monoxide in the furnace at 450 °C. I Fe2O3(s) + 3CO(g) 2Fe(s) + 3CO2(g) ∆Gr = –36.2 kJ mol–1 Table 2.1 shows enthalpy change values of some reactions. Table 2.1 Enthalpy change of formation of Fe2O3(s) ∆Hf = –824 kJ mol–1 Enthalpy change of formation of CO(g) ∆Hf = –110 kJ mol–1 Enthalpy change of combustion of C(s) ∆Hc = –394 kJ mol–1 (i) Using the data given, determine the enthalpy change, ∆Hr, for reaction I. [1] (ii) Hence, calculate the entropy change, ∆Sr, for reaction I. [1] (c) Iron can also be obtained from the reduction of iron(II) oxide, FeO, using carbon monoxide. FeO(s) + CO(g) Fe(s) + CO2(g) Given ∆Hro = –11.1 kJ mol–1, and ∆Sro = –15.2 J mol–1 K–1 for this reaction, predict the effect of increasing temperature on the spontaneity for the formation of iron. Explain your answer. ……………………………………………………………………………………………………... ……………………………………………………………………………………………………... ……………………………………………………………………………………………………... ……………………………………………………………………………………………….….[2]

6 ASRJC JC2 PRELIM 2026 9476/02/H2 Do not write in margin (d) Fe2+ acts as a homogeneous catalyst in the exothermic reaction between I–(aq) and S2O82–(aq). (i) Write equations for the reactions that occur when Fe2+(aq) is added to a mixture of I–(aq) and S2O82–(aq). ……………………………………………………………………………………………… ……………………………………………………………………………………………[2] (ii) Fig. 2.2 shows the energy profile diagram for the uncatalysed reaction between I–(aq) and S2O82–(aq). On the same axes, complete the energy profile diagram for the catalysed reaction between I–(aq) and S2O82–(aq) using Fe2+ catalyst. Include labels to show all relevant species, the enthalpy change , H, and the activation energy, Ea, for the catalysed reaction. Fig. 2.2 [2] [Total:11]

7 ASRJC JC2 PRELIM 2026 9476/02/H2 [Turn over Do not write in margin 3 (a) 2-aminobutane, CH3CH(NH2)CH2CH3, is a liquid with Kb = 3.63 × 10−4 mol dm–3. (i) Explain why an aqueous solution of 2-aminobutane is alkaline. Include a relevant equation in your answer. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………[2] (ii) Calculate the pH of 0.10 mol dm–3 of 2-aminobutane. [1] (iii) Explain why a 0.10 mol dm –3 solution of (CH 3CH2)2NH has a higher pH than a 0.10 mol dm–3 solution of CH3CH(NH2)CH2CH3. ………………………………………………………………………………