2022 EJC Prelims Paper 2 (solution with comments)

© EJC [Turn Over EUNOIA JUNIOR COLLEGE JC2 Preliminary Examination 2022 General Certificate of Education Advanced Level Higher 2 CANDIDATE NAME CIVICS GROUP 2 1 – INDEX NUMBER CHEMISTRY Paper 2 Structured Questions 9729/02 15 September 2022 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. 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 2 1 / 20 2 / 20 3 / 18 4 / 17 Total / 75 This document consists of 19 printed pages and 1 blank page.

2 © EJC 9729/02/J2PE/22 For Examiner’s Use 1 The carbon family consists of the elements of Group 14. The elements at the top of the group, carbon to germanium, have very different properties from those at the bottom, tin and lead. For instance, Group 14 elements tend to adopt oxidation states of +4 , whereas the heavier elements, such as tin and lead, exhibit the +2 oxidation state due to the inert pair effect. (a) State the valence shell configuration of Group 14 elements. ................................ ................................ ................................ ................................ [1] Comments: This is generally badly attempted. Many erroneous responses include electron in box diagram, +4, p4, s2p2. (b) One of the contributing factors to the inert pair effect is the unexpected increase in the ionisation energies, after lead, down the group. Explain why the 1st ionisation energies are expected to decrease down the group. ................................ ................................ ................................ ................................ .... ................................ ................................ ................................ ................................ .... ................................ ................................ ................................ ................................ .... ................................ ................................ ................................ ................................ .... ................................ ................................ ................................ ................................ [2] Comments: Generally well done. Candidates were penalised for mistaking that nuclear charge remains unchanged due to same number of valence electrons instead of number of proton