2025 SAJC H2 Chem Prelim P3_Questions

1 [TURN OVER ST. ANDREW’S JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATIONS HIGHER 2 CANDIDATE NAME CLASS 2 4 S CHEMISTRY Paper 3 Free Response Candidates answer on the Question Paper. Additional Materials: Data Booklet 9729/03 15 September 2025 2 hours READ THESE INSTRUCTIONS FIRST Write your name and class on all the work that you hand in. 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. The use of an approved scientific calculator is expected, where appropriate. 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. 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. This document consists of 35 printed pages (including this cover page). For Examiner’s Use Q1 22 Q2 18 Q3 20 Q4 / Q5 20 Total 80

2 [TURN OVER Section A Answer all the questions in this section. 1 (a) Calcium carbide, CaC₂, is an ionic compound primarily used in industry to generate acetylene gas, C2H2, which has numerous applications in welding, cutting and chemical synthesis. reaction 1 CaC2(s) + 2H2O(l) → Ca(OH)2(s) + C2H2(g) (i) The carbon atoms in CaC2 and C2H2 have sp hybridisation and hence they have similar bonding between the two carbon atoms. Explain what is meant by sp hybridisation with reference to the carbon atoms in C2H2. [2] (ii) Suggest how the electrons are arranged in the second shell of sp carbon atom so that the bonding in the two carbon atoms in C2H2 can occur. [2] (iii) Explain, in terms of structure and bonding, why CaC 2 is a solid at room temperature and pressure while C2H2 is a gas. [2] ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… …………………………………………………………………………………

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