2023 CJC H2 Chem Prelims P3 QP

9729/03/CJC JC2 Preliminary Examination 2023 CANDIDATE NAME CLASS 2T CHEMISTRY 9729/03 Paper 3 Free Response 12 September 2023 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. Write in dark blue or black pen. You may use an 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. If additional space is required, you should use the pages at the end of this booklet. The question number must be clearly shown. Section A Answer all the questions. Section B Answer one question. The use of an approved scientific calculat or is expected, where appropriate. A Data Booklet is provided. At the end of examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 28 printed pages For Examiner’s Use Section A Q1 /23 Q2 /17 Q3 /20 Section B Q4 /20 OR Q5 /20 TOTAL 80 Catholic Junior College JC2 Preliminary Examinations Higher 2

2 9729/03/CJC JC2 Preliminary Examination 2023 Section A Answer all the questions in this section. 1 The element lithium and its compounds have been pivotal in th e area of development for clean automotive power, based on the use of lithium-ion batteries in electric vehicles and the potential use of lithium hydride and lithium aluminium hydride in hydrogen fuel cell vehicles. (a) Lithium hydride can be prepared by passing hydrogen gas over heated lithium. The following data will be useful in this question. enthalpy change of formation of LiH(s) = ‒90.5 kJ mol‒1 enthalpy change of atomisation of Li(s) = +159.5 kJ mol‒1 electron affinity of hydrogen atoms = ‒73.0 kJ mol‒1 enthalpy change of formation of AlCl3(s) = ‒704 kJ mol‒1 enthalpy change of formation of LiCl(s) = ‒408.5 kJ mol‒1 (i) Calculate the lattice energy of LiH(s) using relevant data from the above list, together with relevant data from the Data Booklet. [2] (ii) When heated with anhydrous aluminium chloride, lithium hydride forms lithium aluminium hydride, LiAlH4. Lithium chloride is also produced. The enthalpy change for this reaction is –276 kJ per mole of LiAlH4 formed. Write an equation , with state symbols, for this reaction and use it together with the relevant data from the above list to calculate a value for the enthalpy change of formation of LiAlH4. [3] …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….……………………………………………..

3 9729/03/CJC JC2 Preliminary Examination 2023 [Turn over …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. (b) LiAlH4 and sodium borohydride, NaBH 4, are useful reducing agents in organic chemistry. An organic compound W, C3H4O3, undergoes reduction to form X, C3H8O2 and Y, C3H6O3 via LiA lH4 and NaBH 4 respectively. All three compounds W, X and Y form a yellow precipitate when reacted with alkaline aqueous iodine, and all three compounds react with sodium metal. Compounds W and Y also react with Na2CO3(aq), but compound X does not. (i) Identify the structures for W, X and Y. [3] (ii) Predict the structures of the products P and Q of the following reactions. [2] …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….……………………………………………..

4 9729/03/CJC JC2 Preliminary Examination 2023 …………………………………………………….…………………………………………….. ………………………………………………….……………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. (c) Lithium-ion batteries work by the transfer of lithium ions and electrons from the anode to the cathode. At the anode, elemental lithium inserted between graphite layers is oxidised to Li+. The Li+ ions migrate to the cathode via the electrolyte LiBF 4, where they react with cobalt oxide, CoO2, to form lithium cobalt oxide, LiCoO2. This is illustrated in the following diagram in which C‒C‒C‒C is a simplified representation of a layer of carbon atoms in graphite. (i) State the oxidation states of cobalt in CoO2 and LiCoO2. [1] (ii) Construct an equation for the cathode reaction. [1] (iii) Hence, construct the equation for the overall reaction. [1] (iv) The lithium-ion battery is capable of producing an e.m.f. of 3.60V. By using suitable data from the Data Booklet, suggest a value for the Eo for the cathode reaction. [1] ………………………………………………….……………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….……………………………………………..

5 9729/03/CJC JC2 Preliminary Examination 2023 [Turn over ………………………………………………….……………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….…………………………………………….. …………………………………………………….……………………………………………..

6 9729/03/CJC JC2 Preliminary Examination 2023 (d) Aside from its use in lithium-ion batteries, cobalt is also widely used in alloys in gas turbines and aircraft jet engines as these alloys are corrosion