IGCSE Chemistry 2021 0620/23 May/June

IGCSE 2021 0620/23 May/June (pdf)

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1. A gas is released at point P in the apparatus shown.
   Which gas turns the damp universal indicator paper red most quickly?
2. A 1 cm³ sample of substance X is taken. This is sample 1.
   X is then converted to a different physical state and a 1 cm³ sample is taken. This is sample 2.
   Sample 2 contains more particles in the 1 cm³ than sample 1.
   Which process caused this increase in the number of particles in 1 cm³?
3. Which statement about paper chromatography is correct?
4. Element X has 7 protons.
   Element Y has 8 more protons than X.
   Which statement about element Y is correct?
5. A covalent molecule Q contains only six shared electrons.
   What is Q?
6. Which statement explains why metals are malleable?
7. Which statement about isotopes of the same element is correct?
8. The element silicon has the same structure as diamond.
   Which statement about silicon is correct?
9. Three ionic compounds of vanadium have the formulae V₂O, VCl₂ and V₂O₃.
   What is the charge on the vanadium ion in each compound?
10. In separate experiments, electricity was passed through concentrated aqueous sodium chloride and molten lead(II) bromide.
    What would happen in both experiments?

11. The equation for the decomposition of calcium carbonate is shown.
    CaCO₃  CaO + CO₂
    What mass of calcium oxide is produced when 10 g of calcium carbonate is heated?
12. Gas syringe X contains 100 cm³ of hydrogen bromide gas, HBr.
    Gas syringe Y contains 100 cm³ of carbon dioxide gas. The volume of each gas is measured at room temperature and pressure.
    Which statement is correct?
13. Which simple cell produces the most electrical energy?
14. When sulfur is heated it undergoes a ……1…… change as it melts.
    Further heating causes the sulfur to undergo a ……2…… change and form sulfur dioxide.
    Which words complete gaps 1 and 2?
    
15. Four statements about the effect of increasing temperature on a reaction are shown.
    1 The activation energy becomes lower.
    2 The particles move faster.
    3 There are more collisions between reacting particles per second.
    4 There are more collisions which have energy greater than the activation energy.
    Which statements are correct?
16. An example of a redox reaction is shown.
    Zn + Cu²⁺  Zn²⁺ + Cu
    Which statement about the reaction is correct?
17. The equation for the decomposition of hydrogen iodide is shown.
    2HI  H₂ + I₂
    Some bond energies are shown.
    What is the energy change for the reaction?
18. Element X forms an oxide, XO, that neutralises sulfuric acid.
    Which row describes X and XO?
19. Aqueous solutions of sodium sulfate and barium chloride are mixed.
    Which process is used to separate a sample of barium sulfate from the reaction mixture?
20. Information about element J is shown.
    ● Its atoms have four electrons in their outer shell.
    ● It is a non-metal.
    ● Its oxide has a macromolecular structure.
    ● It has a high melting point.
    What is J?
21. Which property is shown by transition elements?
22. Helium and neon exist as monoatomic gases at room temperature and pressure.
    statement 1 Helium and neon have eight electrons in their outer shell.
    statement 2 Helium and neon are unreactive.
    Which option is correct?
23. What are possible effects of an inadequate water supply during a drought?
    1 crop failure
    2 wastage of water
    3 human disease
    4 death of farm animals
24. Which statement explains why galvanising prevents iron from rusting?
25. Some metal nitrates and carbonates decompose when heated strongly.
    Metal Q has a nitrate that decomposes to give a salt and a colourless gas only.
    The carbonate of metal Q does not decompose when heated with a Bunsen burner.
    What is metal Q?
26. Which compounds are released by the extraction of zinc from zinc blende and by respiration?
27. Which gas is an air pollutant that causes acid rain?
28. Ammonia is made from nitrogen and hydrogen. The equation for the reaction is shown.
29. Which reaction does not occur during the extraction of iron from hematite in a blast Which substance is used as a catalyst in the manufacture of sulfuric acid by the Contact process?
30. Metal X is a good conductor of electricity and is used for electrical wiring.
    Metal Y is used to make an alloy which is resistant to corrosion and is used to make cutlery.
    Metal Z is light and strong and is used in the manufacture of aircraft.
    What are X, Y and Z?
31. The formulae of two compounds of manganese are MnO₂ and KMnO₄.
    In these two compounds the oxidation state of potassium is +1 and the oxidation state of oxygen is –2.
    What are the oxidation states of manganese in each of these two compounds?
32. Which statement about calcium carbonate is correct?
33. Ethanol is reacted with acidified potassium manganate(VII).
    Which row describes the type of reaction and the type of organic compound formed?
34. The diagrams show the structural formulae of four compounds.
35. Which statement about alkanes is correct?
36. How much hydrogen is needed to react completely with 0.02 moles of butene to make butane?
37. What is an advantage of the fermentation process for producing ethanol compared with the catalytic addition of steam to ethene?
38. The structure of a synthetic polymer is shown.
39. Which substance is a natural polymer?

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