2021 EJC Prelims Paper 3 (Solutions with comments)

© EJC [Turn Over EUNOIA JUNIOR COLLEGE JC2 Preliminary Examination 2021 General Certificate of Education Advanced Level Higher 2 CANDIDATE NAME CIVICS GROUP 2 0 – INDEX NUMBER CHEMISTRY Paper 3 Free Response 9729/03 22 September 2021 2 hours Candidates answer on the Question Paper Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, civics group, index number 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 addition 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 calculator is expected, where appropriate. A Data Booklet is provided. 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 Paper 3 Section A 1 / 20 2 / 20 3 / 20 Section B 4 / 20 5 / 20 Total / 80 This document consists of 32 printed pages.

2 © EJC 9729/03/J2PE/21 Section A Answer all the questions in this section. 1 Halogens are powerful oxidising agents, and the oxidising power of halogens may be understood via the energy cycle in Fig. 1.1. Fig. 1.1 The corresponding values of some of the energy terms are given in Table 1.1. Table 1.1 energy term I (kJ mol–1) energy term II (kJ mol–1) energy term III (kJ mol–1) F +79 –328 –506 Cl +121 –349 –364 Br +112 –324 –335 I +107 –295 –293 (a) (i) Name the three energy terms, I, II and III. [2] (ii) Explain why energy term I becomes less endothermic moving down the group from chlorine to iodine. [1] (iii) Explain the exceptionally low value for energy term I of fluorine, in contrast to that of the remainder of the halogens. [1] (iv) Explain why energy term II becomes less exothermic moving down the group from chlorine to iodine. [1] (v) Using values from the Data Booklet, account for the difference in the value of energy term III. [2] ................................ ................................ ................................ ........................... ................................ ................................ ................................ ........................... ................................ ................................ ................................ ........................... ................................ ................................ ................................ ........................... I II III Hr (i) I: enthalpy change of atomisation II: first electron affinity III: enthalpy change of hydration

3 © E