JPJC 2023 Prelim P3 QP

© Jurong Pioneer Junior College [Turn Over NAME CLASS 22S JURONG PIONEER JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION 2023 CHEMISTRY 9729/03 Higher 2 Paper 3 Free Response 13 September 2023 2 hour Candidates answer on the Question paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, class and index number in the spaces at the top of this page. 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. 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 questions. Section B Answer one question. Write the Question number of the Question you have attempted, in the box provided below. A Data Booklet is provided. The use of an approved scientific calculator is expected, where appropriate. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 20 2 22 3 18 4 or 5 20 Penalty (delete accordingly) Lack 3sf in final answer –1 / NA Missing/wrong units in final ans –1 / NA Bond linkages –1 / NA Total 80 This document consists of 32 printed pages.

2 © Jurong Pioneer Junior College 9729/03/J2 PRELIMINARY EXAM/2023 Section A Answer all the questions in this section. 1 Carbon monoxide, CO, occurs in the exhaust gases of internal combustion engines. Other gases in the exhaust gases include oxides of nitrogen, NOx. For Examiner’s Use (a) CO and NO can be removed from the exhaust gases by a catalytic converter to form CO2 and N2. Construct a balanced equation for this reaction. [1] …………………………………………………………………………………………… (b) Explain why N 2 gas behaves more like an ideal gas than CO gas at 20.0 C and 101 kPa. [2] …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… (c) A mixture of carbon monoxide and hydrogen is known as synthesis gas . Synthesis gas is used as a feedstock for the manufacture of methanol. CO(g) + 2H2(g)  CH3OH(g) H = −91.0 kJ mol−1 A temperature of 550 K and pressure of 60 atm are used in this reaction with a catalyst. When the reaction reached equilibrium, a mixture of gases was extracted. It contained 364 g of carbon monoxide, 5 g of hydrogen, and 171 g of methanol. (i) Calculate the value of Kp for this reaction at 550 K. [3] (ii) Explain the effect of increasing temperature on the equilibrium yield of methanol. [1] ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. …………………………………………………………………………………….

3 © Jurong Pioneer Junior College 9729/03/J2 PRELIMINARY EXAM/2023 [Turn Over ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. For Examiner’s Use

4 © Jurong Pioneer Junior College 9729/03/J2 PRELIMINARY EXAM/2023 (d) Liquid methanol could be used instead of petrol in a conventional internal combustion engine. For Examiner’s Use (i) Some enthalpy changes are given in Table 1.1. Table 1.1 H /kJ mol−1 standard enthalpy change of formation of CO2(g) −394 standard enthalpy change of formation of H2O(l) −286 standard enthalpy change of formation of CO(g) −111 standard enthalpy change of CO(g) + 2H2(g) → CH3OH(l) −129 Use the enthalpy changes provided in Table 1.1 to construct a fully labelled energy cycle to find the standard enthalpy change of combustion of liquid methanol, Hc (CH3OH(l)). [3] (ii) Both methanol and synthesis gas can be used as fuels. Suggest one advantage in converting synthesis gas to methanol. [1] ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. …………………………………………………………………………………….

5 © Jurong Pioneer Junior College 9729/03/J2 PRELIMINARY EXAM/2023 [Turn Over ……………………………………………………………………………………. (e) Carbon monoxide reacts with benzene in the presence of hydrogen chloride and aluminium chloride in the Gattermann-Koch reaction to give benzaldehyde. In this reaction, CO and HCl react to form methanoyl chloride, HCOCl. Similar to how A lCl3 generates the electrophile in the halogenation of benzene, AlCl3 reacts with HCOCl, producing a carbocation that can then attack a benzene ring. For Examiner’s Use (i) Suggest an equation for the formation of the carbocation that functions as an electrophile for the Gattermann-Koch reaction. [1] (ii) Suggest the mechanism for the Gattermann -Koch reaction to form benzaldehyde from benzene. In your answer, include the movement of electron pairs using curly arrows. [2] (iii) The Gattermann -Koch reaction is a substitution reaction. Explain why benzene undergoes substitution more readily than addition reaction. [1] ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. …………………………………………………………………………………….

6 © Jurong Pioneer Junior College 9729/03/J2 PRELIMINARY EXAM/2023 (f) Carbon monoxide and methanol are used in an industrial process to form methyl methacrylate . An alternative route to obtain methyl methacrylate from propanone is proposed in Fig. 1.1. For Examiner’s Use Fig. 1.1 (i) Suggest the structures of compounds A, B and C. [3] (ii) Suggest reagents and conditions for step 1 and for step 3. [2] ……………………………………………………………………………………. ……………………………………………………………………………………. …………………………………………………………………………………….