IGCSE Chemistry 2020 0620/21 May/June

IGCSE 2020 0620/21 May/June (pdf)

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1. A mixture of ice and water is left to stand and the ice melts.
   Which row describes what happens as the ice is melting?
2. Which piece of apparatus should be used to measure exactly 21.4 cm³ of water?
3. The chromatogram for an unknown dye is shown.
   What is the R_f value of the dye?
   
4. The atomic number and nucleon number of a potassium atom are shown.
   How many protons, neutrons and electrons are in a potassium ion, K⁺?
   
5. The electronic structures of two atoms, P and Q, are shown.
   P and Q combine together to form a compound.
   What is the type of bonding in the compound and what is the formula of the compound?
   
6. Which row contains a description of metallic bonding and a property that is explained by reference to metallic bonding?
   
7. Which statement explains why methane has a lower boiling point than water?
   
8. A solution of iron(III) sulfate reacts with aqueous sodium hydroxide to form a red–brown precipitate.
   
9. What is the balanced equation, including state symbols, for the reaction?
   The Haber process is a reversible reaction.
   N₂(g) + 3H₂(g) ⇄ 2NH₃(g)
   The reaction has a 30% yield of ammonia.
   Which volume of ammonia gas, NH₃, measured at room temperature and pressure, is obtained by reacting 0.75 moles of hydrogen with excess nitrogen?
   
10. Dilute aqueous sodium chloride is electrolysed using platinum electrodes.
    What is the half-equation for the reaction at the cathode?

11. The electrolysis of aqueous copper(II) sulfate, using inert electrodes, is shown.
    Which statement about a reaction at an electrode is correct?
    
12. The equation for the complete combustion of methane gas is shown.
    CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g)
    Bond energies are shown.
    What is the overall energy change, in kJ /mol, for the above reaction?
    
13. Which statements about hydrogen fuel cells are correct?
    
14. Which diagram represents a chemical change?
    
15. The rate of reaction between calcium carbonate chips and hydrochloric acid is studied by collecting the volume of gas released in one minute at different temperatures.
    A graph of rate of reaction against temperature is shown.
    Which statement fully explains why increasing the temperature has this effect on the rate?
    
16. The equation shows the equilibrium between dinitrogen tetroxide, N₂O₄, and nitrogen dioxide, NO₂.
    The colours of the reactant and product are also shown.
    N₂O₄(g) ⇄ 2NO₂(g)
    The forward reaction is endothermic.
    Which statement is not correct?
    
17. The equations for two reactions of iodide ions are shown.
    
18. The graph shows how the pH of a solution changes as an acid is added to an alkali.
    acid + alkali → salt + water
    Which letter represents the area of the graph where both acid and salt are present?
    
19. Which statement describes a weak acid?
    
20. The apparatus shown is used to prepare aqueous copper(II) sulfate.
    
21. Lead(II) sulfate is an insoluble salt.
    Which method is suitable for obtaining solid lead(II) sulfate?
    
22. A Group I metal (lithium, sodium or potassium) is reacted with a Group VII element (chlorine, bromine or iodine).
    Which compound is formed when the Group I metal of highest density reacts with the Group VII element of lowest density?
    
23. The properties of the element titanium, Ti, can be predicted from its position in the Periodic Table.
    Which row identifies the properties of titanium?
    
24. A balloon is filled with helium. Helium is a noble gas and makes the balloon rise up in the air.
    The density of air is 1.23 g /dm³.
    Which gas is helium?
    
25. Which property is shown by all metals?
    
26. Sodium nitrate is a white crystalline solid that decomposes on heating.
    Which row describes the decomposition products formed when sodium nitrate is heated strongly?
    
27. Molten iron from the blast furnace contains impurities.
    The process of turning the impure iron into steel involves blowing oxygen into the molten iron and adding calcium oxide.
    What are the reasons for blowing in oxygen and adding calcium oxide?
    
28. Element Y reacts with copper(II) oxide to form copper.
    Element Y will not react with zinc oxide. Copper has no reaction with zinc oxide.
    What is the order of reactivity of these three elements, most reactive first?
    
29. Which statement shows that a liquid is pure water?
    
30. Which process removes carbon dioxide from the atmosphere?
    
31. Ammonia is manufactured by the Haber process.
    What are the conditions used in the Haber process?
    
32. Coating iron helps to prevent rusting.
    Which coating will continue to protect the iron even when the coating is damaged?
    
33. A student suggests three uses of calcium carbonate (limestone).
    1 manufacture of cement
    2 manufacture of iron
    3 treating alkaline soils
    Which suggestions are correct?
    
34. The Contact process is used to manufacture concentrated sulfuric acid and consists of four steps.
    Which step involves a catalyst?
    
35. Which row about the production of ethanol by fermentation is correct?
    
36. Which statement about homologous series is correct?
    
37. Increasing the number of atoms in one molecule of a hydrocarbon increases the amount of energy released when it burns.
    What is the correct order?
    
38. Some properties of an organic compound J are listed.
    

• It is a liquid at room temperature.
• It is soluble in water.
• A solution of J reacts with calcium carbonate to form carbon dioxide.
• A solution of J has a pH of 3.
  In which homologous series does J belong?
  

39. Ethane, C₂H₆, reacts with chlorine in a substitution reaction. What are the products of this reaction?
40. Which polymers or types of polymer are synthetic?

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