SJI 2023 Y4 Prelim Chemistry Paper 2

ST JOSEPH’S INSTITUTION PRELIMINARY EXAMINATION 2023 (YEAR 4) CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY Paper 2 Candidates answer on the Question Paper. No Additional Materials are required. 6092/02 18 August 2023 1 hour 45 minutes (10:45 – 12:30) READ THESE INSTRUCTIONS FIRST Write your name, class and index number on all the work you hand in. Write in dark blue or black fluid ink pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, glue or correction fluid. Section A Answer all questions in the spaces provided. Section B Answer all three questions. The last question is in the form either/or. Answer all questions in the spaces provided. The number of marks is given in brackets [ ] at the end of each question or part question. The use of an approved scientific calculator is expected, where appropriate. A copy of the Periodic Table is printed on page 2. For Examiner’s Use Section A / 50 Section B / 30 Total / 80 This document consists of 28 printed pages including this cover page.

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3 Section A (50 marks) Answer all questions in this section in the spaces provided. A1 The names of some aqueous salts are shown below. aluminium sulfate ammonium chloride calcium chloride magnesium sulfate silver nitrate sodium iodide zinc nitrate Use the names of the salts to answer the following questions. You may use each salt once, more than once or not at all. (a) Which salt(s) undergo a redox reaction when reacted with bromine gas? ……………….…………………………………………………………………… ……..[1] (b) Which two salts react with each other to form a yellow precipitate? ……………….…………………………………………………………………………..[ 1] (c) Which salt(s) form a precipitate which is soluble in excess aqueous sodium hydroxide? ……………….…………………………………………………………………………..[1] (d) Which salt(s) form an alkaline gas when heated with excess aqueous sodium hydroxide and aluminium foil? ……………….…………………………………………………………………………..[ 1] [Total: 4]

4 A2 ‘Lean burn’ engines are a type of car engine. Table 2. 1 shows some information about lean burn engines compared to normal car engines. Table 2.1 type of engine amount of air mixed with petrol operating temperature concentration of CO in exhaust gases concentration of nitrogen oxides in exhaust gases normal less air higher higher higher lean burn more air lower lower lower (a) Suggest why lean burn engines produce lower amounts of carbon monoxide. ..………………..…………………………………………………………………………… ……………….…………………………………………………………………………..[ 1] (b) (i) State one natural process that forms nitrogen oxides. ………………..……………………................................................................[1] (ii) Explain why and how lean burn engines produce lower amounts of nitrogen oxides. ……………..………………………………………………………………………… ……………..………………………………………………………………………… ………………..……………………................................................................[2] [Total: 4]

5 A3 Table 3.1 shows some properties of the elements in Group III of the Periodic Table. Table 3.1 element proton number melting point / °C B 5 2306 Al 13 660 Ga 31 30 In 49 157 Tl 81 304 Nh 113 (a) Nihonium, Nh, has only recently been discovered. It has not been possible to directly measure nihonium’s melting point, as it is very radioactive. Suggest why it is also difficult to estimate nihonium’s melting point using the data provided in Table 3.1. ..………………..…………………………………………………………………………… ……………….…………………………………………………………………………..[ 1] (b) Aluminium and sodium are Period 3 elements. Aluminium has an electrical conductivity of 3.50 x 10 7 Siemens per meter (S/ m), while sodium has an electrical conductivity of 2.15 x 107 S/m. Explain why aluminium has a different electrical conductivity from sodium. ..………………..…………………………………………………………………………… ……………….…………………………………………………………………………..[ 1]

6 (c) Boron reacts with chlorine gas to form boron trichloride, BCl3. Boron trichloride has a melting point of -107 °C. In boron trichloride, the boron atom does not ha ve a fully-filled valence electron shell. (i) Draw a ‘dot-and-cross’ diagram to show the bondi ng in boron trichloride. Show valence electrons only. [2] (ii) Using ideas about structure and bonding, explain why boron h as a much higher melting point than boron trichloride. ……………..………………………………………………………………………… ……………..………………………………………………………………………… ……………..………………………………………………………………………… ……………..………………………………………………………………………… ……………..………………………………………………………………………… ……………..………………………………………………………………………… ……………..………………………………………………………………………… ………………..……………………................................................................[3] [Total: 7]

7 A4 Fig. 4.1 shows a simple cell, which can be used to generate electrical energy. Fig. 4.1 (a) Write an ionic equation for the reaction at the silver electrode. Hence, using ideas abo ut electron transfer, expla in if oxidation or r eduction occurs at the silver electrode. ..………………..…………………………………………………………………………… ..………………..…………………………………………………………………………… ……………….…………………………………………………………………………..[ 2] (b) State one change that can be observed in the electrolyte. ……………….…………………………………………………………………………..[ 1] (c) John replaced the copper electrode with a lead electrode. (i) A higher voltmeter reading was immediately observed across the lead-silver cell. Explain why. ……………..………………………………………………………………………… ………………..……………………................................................................[1] (ii) John also tested the electrical conductivity of the electrolyte. He realised that using a lead-silver cell caused the electrical conductivity of the electrolyte to decrease over time. Explain why. ……………..………………………………………………………………………… ……………..………………………………………………………………………… ………………..……………………................................................................[2] [Total: 6] voltmeter silver electrode aqueous sodium sulfate copper electrode

8 A5 This question is about metals. (a) The statements below describe metal X. • X does not react with cold water. • X fizzes slowly with dilute hydrochloric acid. • X does not react with aqueous sodium chloride. • X reacts with aqueous lead(II) nitrate and aqueous silver nitrate. (i) Arrange the following metals in order of reactivity. lead, magnesium, silver, sodium, X most reactive ………………………..……………………… ……………………..………………………… ………………………………..……………… ………………………………..……………… least reactive ……………………………………………….. [1] (ii) Suggest a possible identity for metal X. ………………..……………………................................................................[1] (iii) Using your answer in (a)(ii), write a chemical equation for the reaction between metal X and copper(II) oxide. [1] (iv) Explain your answer in (a)(iii). ……………..………………………………………………………………………… ………………..……………………................................................................[1]

9 (b) Iron is a transition element while potassium is a Group I element. (i) State one difference in physical property between iron and potassium. ……………..………………………………………………………………………… ………………..……………………................................................................[1] (ii) Zinc is used to galvanise iron to prevent the iron from rusting. Explain how galvanising prevents iron from rusting.