IGCSE Chemistry 2018 0620/21 May/June

IGCSE 2018 0620/21 May/June (pdf)

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1. A student investigated the diffusion of ammonia gas, NH₃, and hydrogen chloride gas, HCl.
   Two sets of apparatus were set up as shown at room temperature and pressure.
   The damp red litmus paper in apparatus 1 changed colour after 30 seconds.
   How long does it take for the damp blue litmus paper to change colour in apparatus 2?
   
2. Chromatography is a technique used to separate coloured dyes.
   Which dye has an R_f value of 0.7?
   
3. Which piece of apparatus is used to measure exactly 26.3 cm³ of a liquid?
   
4. The ‘lead’ in a pencil is made of a mixture of graphite and clay.
   When the percentage of graphite is increased, the pencil slides across the paper more easily.
   Which statement explains this observation?
   
5. Chlorine exists as two common isotopes, ³⁵Cl and ³⁷Cl.
   Information about these two isotopes is shown.
   Which statement explains why the two isotopes are of the same element?
   
6. Which substance is not a macromolecule?
   
7. Copper is a metallic element.
   Which statements about copper are correct?
   
8. The equation for the combustion of ethane is shown
   2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O
   Which volume of carbon dioxide, at room temperature and pressure, is formed when 0.5 moles of ethane burn?
   
9. A solution of ethanoic acid, CH₃COOH, has a concentration of 2 mol/dm³.
   Which statement about this solution is correct?
   
10. Aqueous copper(II) sulfate is electrolysed using copper electrodes.
    Which statement is correct?
    
11. Dilute sulfuric acid is electrolysed using inert electrodes.
    What are the ionic half-equations for the reactions that take place at each electrode?
    
12. Plant cells use energy from sunlight for photosynthesis.
    Which row describes and explains the energy change that occurs?

13. Hydrogen bromide decomposes to form hydrogen and bromine. The equation is shown.
    2HBr(g) → H₂(g) + Br₂(g)
    The bond energies are shown in the table. The reaction is endothermic.
    What is the energy change for the reaction?
    
14. Which row describes the effects of increasing both concentration and temperature on the collisions between reacting particles?
    
15. The formation of sulfur trioxide is a reversible reaction.
    The equation is shown.
    2SO₂(g) + O₂(g) ⇄ 2SO₅(g)
    The forward reaction is exothermic.
    Which conditions produce the highest equilibrium yield of sulfur trioxide?
    
16. Chlorine displaces iodide ions from potassium iodide.
    Cl₂ + 2I^– → I₂ + 2Cl^–
    What is the oxidising agent?
    
17. Which statement about oxides is correct?
    
18. Which solution has the lowest pH?
    
19. A student mixes silver nitrate and barium chloride to form a white precipitate of silver chloride.
    The equation is shown.
    2AgNO₃ + BaCl₂ → 2AgCl + Ba(NO₃)₂
    Which row describes the solubility of the salts?
    
20. Which methods are suitable for preparing both zinc sulfate and copper(II) sulfate?
    
21. Which element is in the same period of the Periodic Table as silicon?
    
22. Which statement about the halogens is correct?
    
23. Which row shows the catalytic activity of transition elements and their compounds?
    
24. The following statements are made about the metals copper, iron, magnesium and zinc.
    
25. Silver is a less reactive metal than cadmium.
    Cadmium is a less reactive metal than barium.
    Which statement is correct?
    
26. Aluminium metal is extracted from aluminium oxide using electrolysis.
    Which statement about the extraction process is not correct?
    
27. Which statement explains why aluminium is used in the manufacture of aircraft?
    
28. Dry air is passed over hot copper until all the oxygen has reacted
    The volume of gas at the end of the reaction is 120 cm³.
    What is the starting volume of dry air?
    
29. A steel bicycle which had been left outdoors for several months was starting to rust.
    What would not reduce the rate of corrosion?
    
30. Which statements about water are correct?
    
31. Ammonia is manufactured by reacting hydrogen with nitrogen in the Haber process.
    Which row describes the sources of hydrogen and nitrogen and the conditions used in the manufacture of ammonia in the Haber process?
    
32. Which statements about the carbon cycle are correct?
    
33. Which statement about sulfur and its compounds is not correct?
    
34. Which process is used to convert limestone (calcium carbonate) into lime?
    
35. What is not the correct use of the fraction named?
    
36. Which reaction is not a reaction which alkenes undergo?
    
37. Which substances can be obtained by cracking hydrocarbons?
    
38. Ethanol is produced by fermentation or from ethene.
    What is a disadvantage of producing ethanol by fermentation?
    
39. Which structural formula represents methyl propanoate?
    
40. Which row describes addition polymerisation and condensation polymerisation?

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