2023 RI Prelim H2 Chem Paper 2 Question Paper

© Raffles Institution 2023 9729/02/S/23 [Turn Over RAFFLES INSTITUTION 2023 YEAR 6 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY 9729/02 Paper 2 Structured Questions 13 September 2023 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Do not open this question booklet until you are told to do so. Write your name, class and index number in the spaces provided at the top of this 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. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. Do not write anything in it. You are reminded of the need for good English and clear presentation in your answers. 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 1 / 10 2 / 13 3 / 15 4 / 11 5 / 14 6 / 12 Total / 75 This document consists of 23 printed pages and 1 blank page.

2 © Raffles Institution 2023 9729/02/S/23 [Turn Over Answer all the questions in the spaces provided. 1 (a) Chlorine is an element in Group 17 of the Periodic Table. Describe and explain how the volatilities of the halogens vary from chlorine to iodine. …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… ……………………………………………………………………………………….. [2] (b) X has the formula PCl3+ and contains 31P, 35Cl and 37Cl. X is unstable and breaks down into two fragments, Y and Z. (i) Complete Table 1.1 to describe the characteristics of these particles. Table 1.1 X Y Z nucleon number 140 37 charge +1 +1 [1] X and Y were fired with equal velocity into an electric field. Fig. 1.1 (ii) On Fig. 1.1, draw the paths taken by particles X and Y as they pass through the electric field. Label your drawing clearly. [1]

3 © Raffles Institution 2023 9729/02/S/23 [Turn Over (iii) Deduce the number of 35Cl atoms in a particle of Y and give the shape of Y. number of 35Cl atoms in Y …………………………. shape of Y …………………………………………… [2] Electron affinity is a measure of the electrostatic attraction between an incoming electron and the nucleus – the stronger the attraction, the more energy is released. The first electron affinity o f an element is the energy change when one mole of gaseous atoms acquires one mole of electrons to form one mole of singly negatively charged gaseous ions. Fig. 1.2 shows the trend in the first electron affinities of the elements aluminium to chlorine. Fig. 1.2 (c) (i) Write an equation for the first electron affinity of phosphorus. ……………………………………………………………………………….. [1] (ii) Complete the diagram to show the arrangement of electrons in the orbitals of the anion formed in (c)(i). 1s 2s 2p 3s 3p [1] -400 -350 -300 -250 -200 -150 -100 -50 0 Al Si P S Cl element first electron affinity / kJ mol–1 Al Si P S Cl 0 −50 −100 −150 −200 −250 −300 −350 −400

4 © Raffles Institution 2023 9729/02/S/23 [Turn Over (iii) The magnitude of the first electron affinity generally increases from aluminium to chlorine.  In terms of nuclear charge and shielding effect, provide an explanation for this general trend. ………………………………………………………………………........ ………………………………………………………………………........ ………………………………………………………………………... [1]  Suggest why phosphorus does not follow this trend. ………………………………………………………………………........ ………………………………………………………………………... [1] [Total: 10]

5 © Raffles Institution 2023 9729/02/S/23 [Turn Over 2 Gold is a transition element in Period 6. (a) Suggest why gold has a higher density than barium. …………………………………………………………………………………………… ……………………………………………………………………………………….. [1] In small-scale gold mining, mercury is often used to extract gold from its ore. Mercury captures fine gold particles to form an amalgam, which is a soft, solid mixture of the two metals. (b) A gold-mercury amalgam formed typically contains between 40% and 80% of mercury by mass. In a particular extraction, 250 g of amalgam was obtained from 20 kg of ore. Calculate the maximum mass of gold present in the amalgam. [1] To recover the gold from the amalgam, the solid is heated to vaporise the mercury which escapes into the atmosphere. (c) Determine the concentration, in ppm, of mercury vapour in a 1 m3 space if just 1 g of mercury is released into the atmosphere. Density of air = 1.19 kg m–3 (1 ppm of Hg = 1 g of Hg in 106 g of air) [1]

6 © Raffles Institution 2023 9729/02/S/23 [Turn Over Mercury is volatile and vapour concentrations above 0.001 ppm are considered hazardous to human health. To reduce mercury emission from the heating process , as well as to recover the mercury, two possible methods have been recommended to help the gold miners, who are often from poverty-stricken communities. Method I Method II (The above diagrams are not drawn to scale.) (d) (i) For Method I, besides cooling down the stainless steel tube, explain why water is needed. ………………………………………………………………………………... [1] (ii) Suggest how Method II allows mercury to be recovered from the amalgams. ………………………………………………………………………………........ ………………………………………………………………………………... [1] (iii) State one advantage and one disadvantage of Method II as compared to Method I. advantage ….…………………………………………………………………... ….…………………………………………………………………..................... disadvantage .………………………………………………………………….. ….…………………………………………………………………..................... [2]

7 © Raffles Institution 2023 9729/02/S/23 [Turn Over In the presence of oxygen, gold dissolves in an aqueous solution of KCN to form complex anion D and hydroxide ions. (e) (i) Give the half-equation for the reduction of O2 in the above reaction. ………………………………………………………………………………... [1] (ii) In the reaction, 1 mol of O2 oxidises 4 mol of Au. Determine the oxidation state of Au in the complex anion D. oxidation state of Au ……………... [1] (iii) D is a linear anion, with a single gold ion in its structure. It does not contain any oxygen or hydrogen atoms. State the formula of D. ………………………………………………………………………………... [1] (f) (i) State what is meant by the term metallic bond. …………………………………………………………………………………… ………………………………………………………………………………... [1] (ii) The electronic configuration of mercury is [Xe] 4f14 5d10 6s2. Its inner electrons provide poor shielding for its outermost electrons. It has one of the highest first ionisation energy among metals. By considering the information given and your answer in (f)(i), suggest why mercury is a liquid, and not a solid at room temperature. …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… ………………………………………………………………………………... [2] [Total: 13]

8 © Raffles Institution 2023 9729/02/S/23 [Turn Over 3 The rate of hydrolysis of sucrose can be determined experimentally using the continuous experimental method. C12H22O11 + H2O → C6H12O6 + C6H12O6 sucrose gluco