2024 Prelims CJC H2 Chem P2 (Ans)

[Turn over 9729/02 CJC JC2 Preliminary Examination 2024 CANDIDATE NAME CLASS 2T INDEX CHEMISTRY 9729/02 Paper 2 Structured Questions 26 August 2024 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name and class 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. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 16 printed pages. For Examiner’s Use Paper 1 30 Paper 2 Q1 /7 Q2 /11 Q3 /13 Q4 /15 Q5 /15 Q6 /14 75 Paper 3 80 Paper 4 55 OVERALL (100%) GRADE Catholic Junior College JC2 Preliminary Examination Higher 2 WORKED SOLUTIONS WORKED SOLUTIONS

2 9729/02 CJC JC2 Preliminary Examination 2024 Answer all the questions in the space provided. 1 Tetrahalosilanes have the general formula SiX4, where X represents one of the halogens. A sample of SiX4 is atomised and ionised. The ions produced are then analysed. (a) Complete the following energy level diagram to show the arrangement of electrons in the orbitals of Si+ ion. [2] (b) In the first analysis, the second ionisation energy of silicon is recorded. Write an equation for the second ionisation energy of silicon. ……..……………………………………………………………………………………….. [1] (c) Explain why the second ionisation energy of silicon is higher than that of the first. …………………..…………………………………………………………………………...… ……….…….………………………………………………………………………….......…… .…..…………………………………………………………………………………………….. .................................................................................................................................. [1] Energy 1s 2s 3p 3s 2p Si+(g) → Si2+(g) + e– The increase in the second ionisation energy is due to more energy required to remove the second electron from an ion with the same nuclear charge as the atom but attracting fewer electrons due to stronger electrostatic force of attraction between the nucleus and valence electrons.

3 9729/02 CJC JC2 Preliminary Examination 2024 [Turn over (d) In the second analysis, ions of X+ are analysed. A sample each of 28 + 14Si and X+ is passed through an electric field. The angles of deflecti