2020 SNGS Prelim P2

This document consists of 20 printed pages. [Turn over Name: _________________________ ( ) Class:_____________ PRELIMINARY EXAMINATION GENERAL CERTIFICATION OF EDUCATION ORDINARY LEVEL ______________________________________________________________ CHEMISTRY 6092/02 Paper 2 26 August 2020 1hour 45minutes ______________________________________________________________ READ THESE INSTRUCTIONS FIRST Write your name, register number, and class clearly in the spaces provided at the top of this page. Write in dark blue or black pen only. You may use a soft pencil for any diagrams or graphs. Do not use highlighters, glue, and correction fluid or correction tape. Section A Answer all questions in the spaces provided. Section B Answer all three questions, the last question is in the form of either/or. Answer all questions in the spaces provided. A copy of Periodic Table is provided on page 2. The number of marks is given in brackets [ ] at the end of each question or part question. The use of a scientific calculator is expected, where appropriate. Marks Section A (50) Section B (30) Total (80)

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3 Section A Answer all the questions in this section in the space provided. The total mark for this section is 50. A1 The following substances are given: aluminium lithium oxide water air zinc oxide ammonium chloride brass silver carbonate nitrogen monoxide Each substance may be used once, more than once or not at all. (a) (i) Which substance is a mixture of elements only? ……………………………………………………………………………………………..[1] (ii) Which substance contains a non-metallic element with an oxidation state of +2? ……………………………………………………………………………………………..[1] (iii) Which substance reacts with hot alkaline sodium nitrate to form an alkaline gas? ……………………………………………………………………………………………..[1] (iv) Which substance can be obtained by sublimation when mixed with sodium chloride? ……………………………………………………………………………………………..[1] (v) Which substance is best obtained by simple distillation when mixed with ammonium chloride? ……………………………………………………………………………………………..[1]

4 (b) Briefly describe how a sample of pure and dry silver carbonate can be produced in the laboratory. ……………………………………………………………………………………………................ ……………………………………………………………………………………………................ ……………………………………………………………………………………………................ ……………………………………………………………………………………………............[3] [Total: 8 marks] A2 Elements R and Q react with chlorine readily to form chl orides. The table below below shows some of the properties of the two chlorides, RCl2 and QCl2. RCl2 QCl2 melting point/oC 874 -120 boiling point /oC 1250 59 electrical conductivity of liquid good poor solubility in water dissolves to form a neutral solution reacts to form a solution of pH 1 (a) Describe the arrangement and movement of particles in QCl2 at 30oC. …………………………………………………………………………………………................[1] (b) Which groups of the Periodic Table do R and Q belong to? ……………………………………………………………………………………………................ ……………………………………………………………………………………………............[2]

5 (c) Explain in terms of bonding and structure the difference in electrical conductivity of liquid RCl2 and liquid QCl2. ……………………………………………………………………………………………................ ……………………………………………………………………………………………................ ……………………………………………………………………………………………................ ……………………………………………………………………………………………................ ……………………………………………………………………………………………............[4] (d) When QC l2 is added to water , the r esulting mixture has pH 1 . Suggest the name of a compound formed during the reaction. ……………………………………………………………………………………………............[1] (e) Suggest the formula of a covalent compound which has a boiling point of 2230oC. ……………………………………………………………………………………………............[1] [Total: 9 marks]

6 A3 This question is about the halogens. (a) The table shows data about the melting and boiling points of three halogens, chlorine, bromine and iodine. Complete the table by filling in the name of each halogen. name of halogen Melting point /oC Boiling point /oC -7.2 58.8 -100.9 -34.7 113.8 184.5 [1] (b) Describe the trend in the reactivity of the elements down Group VII. Explain your answer based on their atomic structures. …………………………………………………………………………………………….................... …………………………………………………………………………………………….................... …………………………………………………………………………………………….................... ……………………………………………………………………………………………................[2] (c) Seawater contains potassium bromide. (i) What would be observed when aqueous chlorine is added to seawater? Explain your answer. ……………………………………………………………………………………………………. ………………………………………………………………………………………………....[2] (ii) Describe a chemical test to show that seawater also contains sulfate ions. ……………………………………………………………………………………………………. ………………………………………………………………………………………………....[2] (d) Chlorine and fluorine react vigorously to form chlorine trifluoride , C lF3. Explain using oxidation numbers, whether chlorine is an oxidising or a reducing agent in this reaction. …………………………………………………………………………………………….................... …………………………………………………………………………………………….................... ……………………………………………………………………………………………................[2] [Total: 9 marks]

7 A4 The graph b elow shows how the mass of a solid in a boiling tube changes as the reaction progresses. stages description I Solid P is heated strongly to form solid Q. A gas is evolved producing white precipitate with limewater. II Excess dilute hydrochloric acid is added to solid Q. III Aqueous ammonia is added to the reaction mixture obtained from stage II. IV Dilute nitric acid and aqueous silver nitrate are added to the reaction mixture obtained from stage III. (a) State the identity of gas produced in stage I. ……………………………………………………………………………………………................[1] (b) Suggest two possible identities of the cations present in solid P. Explain your answer. …………………………………………………………………………………………….................... …………………………………………………………………………………………….................... ……………………………………………………………………………………………................[2] (c) Write a chemical equation for the reaction in stage I. ……………………………………………………………………………………………................[1]

8 (d) Write an ionic equation for the formation of the solid in stage IV. ……………………………………………………………………………………………................[1] (e) Explain why the mass of the soild reaches a constant in stage IV. …………………………………………………………………………………………….................... …………………………………………………………………………………………….................... ……………………………………………………………………………………………................[1] [Total: 6 marks]

9 A5 The diagram below shows the set -up used for the electrolysis of solution X and dilute potassium chloride solution using graphite electrodes. Dilute potassium chloride solution has a pH of 7. (a) Suggest an identity for solution X. ……………………………………………………………………………………………................[1] (b) (i) Write ionic equations for the reactions occuring at electrodes C and D. Electrode C: ………………………………………………………….. Electrode D: ………………………………………………………….. [2] (ii) Suggest one industrial use of the product formed at electrode C. ……………………………………………………………………………………………........[1] (c) After electrol ysing for 20 minutes, 84 cm 3 of gas is collected in the test tube at electrode C at room temperature and pressure. Calculate the mass of copper