2024 Prelims ACJC H2 Chem P3 (QP)

This document consists of 30 printed pages and 2 blank pages. Anglo-Chinese Junior College JC2 Preliminary Examination Higher 2 CANDIDATE NAME FORM CLASS 2 TUTORIAL CLASS 2CH INDEX NUMBER CHEMISTRY Paper 3 Free Response Candidates answer on the Question Paper. Additional Materials: Data Booklet 9729/03 27 August 2024 2 hours READ THESE INSTRUCTIONS FIRST Write your index number and name 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 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. Circle the number of the question you have attempted. A Data Booklet is provided. The use of an approved scientific calculator is expected, where appropriate. 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 Examiners’ use only Section A 1 / 20 2 / 20 3 / 20 Section B 4 / 5 / 20 Presentation Total / 80

2 © ACJC2024 9729/Preliminary Examination/2024 [Turn over Section A Answer all the questions in this section. 1 (a) Describe the variation in the behaviour of Period 3 chlorides NaCl, AlCl3 and PCl5 separately with water. Write equations for any reactions described and state the pH of the resultant solutions. [3] ………………………………………………………………………………………………………… ………………………………………………………………………………………………….…….. ………………………………………………………………………………………………….…….. ………………………………………………………………………………………………….…….. ……………………………………………………………………………………………….……….. ………………………………………………………………………………………………….…….. ………………………………………………………………………………………………….…….. ………………………………………………………………………………………………….…….. ………………………………………………………………………………………………….…….. ………………………………………………………………………………………………….…….. (b) When soil becomes acidic, aluminium leeches out of minerals into the soil. High aluminium content in soil affects root growth and causes the roots to be brittle. These problems are minimised if the topsoil pH is maintained above 5.5. In a study of a soil condition, a sample of soil water was titrated with EDTA4−, a hexadentate ligand, to determine its aluminium ion concentration. equation 1 [Al(H2O)6]3+(aq) + EDTA4−(aq) [Al(EDTA)]−(aq) + 6H2O(l) (i) State the type of reaction in equation 1. [1] (ii) The concentration of aluminium ions in the soil water sample was found to be 2.90 × 10–5 mol dm–3. Calculate the pH of the water sample, given that the aqueous complex of Al3+ has a Ka value of 7.9 × 10–6. You may assume that the complex of Al3+ behaves as a weak monobasic acid, HA. [1] (iii) Another 25 cm3 sample of soil water was found to contain 0.250 mol dm–3 of NaH2PO4. 20 cm3 of solution A which contains aqueous Na2HPO4 was added to the water sample to obtain a solution buffered at pH 6.8. Calculate the concentration of HPO42– in solution A, given that the pKa value of H2PO4– is 7.2. [3]

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4 © ACJC2024 9729/Preliminary Examination/2024 [Turn over (c) The reactions of ethylbenzene to form H, J and K are shown in Fig.1.1. Fig. 1.1 (i) Suggest the reagents and conditions needed for reactions I and II and suggest the structure of M in Fig. 1.1. [3] (ii) Describe and explain the relative ease of hydrolysis of H, J and K. [3] …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………………. …………………………………………………………………………………………………. ………………………………………………………………………………………………….

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6 © ACJC2024 9729/Preliminary Examination/2024 [Turn over (d) Graphene is a nanomaterial comprising of a single layer of graphite. Compared with copper, it has higher tensile strength and similar electrical conductivity while having lower mass. An experiment was conducted to electroplate copper onto graphene. In the experiment, a copper anode and graphene cat