RI Prelim P2 (Qns)

© Raffles Institution 2020 9729/02/S/20 [Turn Over RAFFLES INSTITUTION 2020 YEAR 6 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY 9729/02 Paper 2 Structured Questions 15 September 2020 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Do not open this question booklet until you are told to do so. Write your name, class and index number in the spaces provided at the top of this page. 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. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. Do not write anything in it. You are reminded of the need for good English and clear presentation in your answers. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 / 9 2 / 16 3 / 16 4 / 15 5 / 19 Total / 75 This document consists of 23 printed pages.

2 © Raffles Institution 2020 9729/02/S/20 For examiner’s use Answer all the questions in the spaces provided. 1 (a) The Cannizzaro reaction involves the conversion of aldehyde into a primary alcohol and a carboxylate ion under alkaline conditions. Benzaldehyde is heated with potassium hydroxide to give phenylmethanol and potassium benzoate, as shown in equation 1. (i) State the oxidation numbers of C(1), C(2) and C(3). oxidation number of C(1) = ……………. oxidation number of C(2) = ……………. oxidation number of C(3) = ……………. [2] (ii) Hence, state the type of reaction for equation 1. ………………………………………………………………………………………………. [1] (b) A student suggested performing the Cannizzaro reac tion in a non -alkaline medium as shown in equation 2. equation 2 2C6H5CHO(l) + H2O(l)  C6H5CH2OH(l) + C6H5COOH(s) Table 1.1 shows some data on the standard enthalpy changes of formation, ∆Hf, and standard enthalpy change of vapourisation, ∆Hvap. Table 1.1 ∆Hf of benzaldehyde, C6H5CHO(l) –87.0 kJ mol–1 ∆Hf of phenylmethanol, C6H5CH2OH(l) –160.7 kJ mol–1 ∆Hf of benzoic acid, C6H5COOH(s) –385.2 kJ mol–1 ∆Hvap of water, H2O(l) +44.0 kJ mol–1

© Raffles Institution 2020 9729/02/S/20 [Turn Over 3 For examiner’s use (i) Using relevant data from the Data Booklet, calculate ∆Hf(H2O(g)). [1] (ii) Using the standard enthalpy changes given in Ta ble 1.1 and your answer in (b)(i), draw an appropriate energy cycle and calculate the standard enthalpy change, ∆Hr, for the reaction shown in equation 2.