TMJC_2025_H2 Chem_P3_Answer

CANDIDATE NAME CIVICS GROUP H2 CHEMISTRY 9729/03 Paper 3 Free Response 23 September 2025 2 hours Candidates answer on the Question Paper. Additional materials: Data Booklet This document consists of 30 printed pages and 2 blank pages. TAMPINES MERIDIAN JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION READ THESE INSTRUCTIONS FIRST Write your name and Civics Group in the spaces at the top of the 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. 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. 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 Percentage Paper 1 / 30 / 15 Paper 2 / 75 / 30 Paper 3 Section A 1 / 19 2 / 20 3 / 21 Section B 4 / 20 OR 5 / 20 Paper 3 Total / 80 / 35 Paper 4 / 55 / 20 Grand Total / 100

2 Tampines Meridian Junior College 2025 JC2 Preliminary Examination H2 Chemistry Section A Answer all the questions in this section. 1 (a) Describe and explain the trend in the thermal stabilities of the Group 2 carbonates. [2] ……………………………………………………………………………………………...……. ……………………………………………………………………………………….................. ……………………………………………………………………………………………...……. ……………………………………………………………………………………….................. ……………………………………………………………………………………………...……. ……………………………………………………………………………………………...……. ……………………………………………………………………………………….................. (b) Calcium carbonate is used in flue -gas desulfurisation applications to remove harmful SO2 and NO2 emissions from fossil fuels burnt in power stations. (i) Draw dot-and-cross diagrams to show the bonding in the molecules of SO 2 and NO2. [2] (ii) With reference to your answer in (b)(i), explain why the bond angle in SO2 is found to be 118 while that in NO2 is 134. [2] ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... (b) (i) (ii) For SO2, as there are 2 bond pairs and 1 lone pair around the central S atom. Since lone pair–bond pair repulsion > bond pair – bond pair repulsion. the bond angle is about 118. However, in NO2, the repul