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|Cambridge Assessment, E International Education, TM, Cambridge IGCSE, CANDIDATE, NAME, CENTRE, CANDIDATE, NUMBER, NUMBER, CHEMISTRY, 0620/42, Paper 4 Theory (Extended), May/June 2020, 1 hour 15 minutes, You must answer on the question paper., No additional materials are needed., INSTRUCTIONS, Answer all questions., Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs., Write your name, centre number and candidate number in the boxes at the top of the page., Write your answer to each question in the space provided., Do not use an erasable pen or correction fluid., Do not write on any bar codes., You may use a calculator., You should show all your working and use appropriate units., INFORMATION, The total mark for this paper is 80., The number of marks for each question or part question is shown in brackets [ ]., The Periodic Table is printed in the question paper., This document has 16 pages. Blank pages are indicated., IB20 06 0620 42/4RP, © UCLES 2020, [Turn over, * 73 3 6 6 15 3 18 *

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2, (a) Give the name of the process that:, (i) occurs when a gas turns into a liquid, [1], (ii) occurs when a solid turns into a gas without first forming a liquid, [1], (iii) is used to separate a mixture of liquids with different boiling points, [1], (iv) is used to extract aluminium from aluminium oxide, [1], (v) is used to separate a mixture of amino acids., [1], (b) The symbols of the elements in Period 2 of the Periodic Table are shown., Li, Ве, C NO F, Ne, For each of the following, give the symbol of an element from Period 2 which matches the, description., Each element may be used once, more than once or not at all., Which element:, (i) combines with hydrogen to produce ammonia, [1], (ii) makes up approximately 21% of clean, dry air, [1], (iii) has atoms with only two electrons in the outer shell, [1], (iv) has atoms with only seven protons, [1], (v) is a monoatomic gas, [1], (vi) is a soft metal stored in oil?, [1], [Total: 11], © UCLES 2020, 0620/42/M/J/20

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3, 2, Fluorine forms both ionic and covalent compounds., (a) Magnesium reacts with fluorine to form the ionic compound magnesium fluoride., The electronic structures of an atom of magnesium and an atom of fluorine are shown., *米, Mg, (i) Complete the dot-and-cross diagrams to show the electronic structures of one magnesium, ion and one fluoride ion. Show the charges on the ions., Mg, [3], (ii) What is the formula of magnesium fluoride?, [1], (ii) Magnesium fluoride does not conduct electricity when it is solid., What can be done to solid magnesium fluoride to make it conduct electricity?, In your answer explain why magnesium fluoride conducts electricity when this change is, made., [2], © UCLES 2020, 0620/42/M/J/20, [Turn over

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4, (b) Carbonyl fluoride, COF,, is a covalent compound. The structure of a molecule of COF, is, shown., .F, Complete the dot-and-cross diagram to show the electron arrangement in a molecule of, carbonyl fluoride. Show outer shell electrons only., F, [3], (c) The melting points of magnesium fluoride and carbonyl fluoride are shown., melting point/°C, magnesium fluoride, 1263, carbonyl fluoride, -111, (i) Explain, using your knowledge of structure and bonding, why magnesium fluoride has a, high melting point., [2], (ii) Explain, using your knowledge of structure and bonding, why carbonyl fluoride has a low, melting point., [2], [Total: 13], © UCLES 2020, 0620/42/M/J/20

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5, 3, (a) Sulfuric acid is made from sulfur in a four-stage process., stage 1, Sulfur is converted into sulfur dioxide., stage 2 Sulfur dioxide is converted into sulfur trioxide., stage 3 Sulfur trioxide is converted into oleum., stage 4, Oleum is converted into sulfuric acid., (i) How is sulfur converted into sulfur dioxide in stage 1?, [1], (ii) Describe how sulfur dioxide is converted into sulfur trioxide in stage 2., Your answer should include:, an equation for the reaction, the temperature used, the name of the catalyst used., [3], (iii) The reaction in stage 2 can reach equilibrium., What is meant by the term equilibrium?, (b) Sulfur trioxide is converted into oleum, H,S,07, in stage 3., What is sulfur trioxide reacted with to convert it into oleum?, [1], (c) Oleum is converted into sulfuric acid in stage 4., Write a chemical equation for the conversion of oleum, H,S,07, into sulfuric acid., [2], © UCLES 2020, 0620/42/M/J/20, [Turn over, 2)