Lesson 3.2.3.2

3.2.3.2 Uses of chlorine and chlorate(I) Quiz: AQA Chemistry, Unit 2

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.2.3.2, Uses of chlorine and chlorate(I): 20 multiple choice questions for the AQA Chemistry (7405), Unit 2: Inorganic chemistry, written with Revision Ninja.

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The 20 questions

  1. What happens when chlorine reacts with cold, dilute aqueous sodium hydroxide?

    • Chlorine is unchanged, because it does not react with alkali
    • Sodium chloride, sodium chlorate(I) and water are formed
    • Sodium bromide and oxygen are formed
    • Only sodium chlorate(V) and hydrogen are formed

  2. What is the bleaching solution formed when chlorine reacts with cold dilute sodium hydroxide, and what is its active ion?

    • Sodium chlorate(V), NaClO3, with the chlorate(V) ion as the active species
    • Sodium chloride, NaCl, with the chloride ion as the active species
    • Sodium hydroxide, NaOH, with the hydroxide ion as the active species
    • Sodium chlorate(I), NaClO, with the chlorate(I) ion as the active species

  3. What happens when chlorine dissolves in water?

    • It forms chlorine oxide and hydrogen only, with no ions formed
    • It reacts to form hydrochloric acid and chloric(I) acid, so chloride and chlorate(I) ions are formed
    • It forms oxygen and sodium chloride, which precipitate out of the solution
    • It dissolves without any reaction, forming a neutral solution of chlorine molecules

  4. Which oxygen-containing product is formed when chlorine reacts with water?

    • Oxygen gas, formed from chlorate(I) breakdown in the presence of light
    • Nitrogen dioxide, formed from the reaction with dissolved air
    • Carbon dioxide, formed from the reaction of chlorine with the solvent
    • Sulfur dioxide, formed from the reduction of the water

  5. Why is chlorine used in water treatment?

    • It kills harmful bacteria and microorganisms, making drinking water safe
    • It converts the water into hydrogen and oxygen gas
    • It increases the pH of the water to exactly 14
    • It removes all dissolved salts from the water, making it pure

  6. Which statement about the use of chlorine in water treatment is correct?

    • The toxic effects of chlorine outweigh its benefits, so it is never used in water supplies
    • The benefits to health from killing pathogens outweigh its toxic effects at the levels used
    • Chlorine is used only in swimming pools, and never in drinking water
    • Chlorine is harmless at any concentration, so it has no toxic effects at all

  7. When society decides whether a chemical should be added to a water supply, which factor is weighed?

    • The chemical's effect on the taste of the water alone, since that is what most people notice first
    • The cost of the chemical only, since price is the sole factor that matters in a public water decision
    • The colour of the chemical only, since water supplied to homes must always be perfectly clear to be safe
    • The balance of advantages and disadvantages, including health benefits and possible harms

  8. What is the reaction of chlorine with cold, dilute NaOH used for in the home?

    • Making bleach and cleaning solutions, using the sodium chlorate(I) formed
    • Making sodium metal, which is used in batteries, and this is the main industrial use of the solution formed
    • Producing oxygen for use in breathing apparatus, which is the main industrial use of the solution formed here
    • Producing hydrogen gas for fuel cells in domestic heating systems, which is a major use of chlorine chemistry

  9. In the reaction Cl2 + H2O -> HCl + HClO, what are the oxidation states of chlorine in HCl and HClO respectively?

    • +1 in HCl and -1 in HClO
    • -1 in HCl and +1 in HClO
    • -1 in HCl and -1 in HClO
    • 0 in HCl and +2 in HClO

  10. Which statement describes the disproportionation of chlorine in cold dilute sodium hydroxide?

    • Chlorine is neither oxidised nor reduced, because it is a diatomic molecule
    • Chlorine is only oxidised, forming chlorate(I) ions with no reduction
    • Chlorine is only reduced, forming chloride ions with no other change
    • Chlorine is both oxidised and reduced, forming chloride ions and chlorate(I) ions

  11. Chlorine has an oxidation state of +1 in chlorate(I) ions. What is its oxidation state in chloride ions?

    • -1
    • -2
    • +1
    • 0

  12. Why must the water treatment with chlorine be carefully controlled?

    • Chlorine is toxic at high levels, so the amount added must be kept at the level that kills microbes safely
    • Chlorine is harmless at any level, so the amount added is unimportant
    • Chlorine must be kept below the level that kills microbes, so that it does not harm the water supply
    • Chlorine becomes a gas at high concentrations, which must be kept from the water entirely

  13. Which property of chlorine makes it effective as a disinfectant in water?

    • Its low reactivity, which keeps it in the water for long periods
    • Its strong oxidising power, which destroys the cell structures of microbes
    • Its high boiling point, which keeps it liquid in the water supply
    • Its strong reducing power, which removes oxygen from the water

  14. Why is the addition of sodium fluoride to water supplies considered an issue for society?

    • It involves weighing health benefits against risks and public choice, which society must assess
    • It is a chemical with no effect on health at all, so no assessment of advantages or risks is needed here
    • It is always fatal, so it is banned in every country around the world and is never added to water at all
    • It changes the pH of the water to exactly 14, which is always harmful to health, so it must never be added

  15. Which of these is a use of chlorate(I) solutions?

    • Generating electricity in a fuel cell
    • Bleaching and disinfecting
    • Making steel from iron ore
    • Producing fertiliser by the Haber process

  16. What is the ionic equation for the reaction of chlorine with cold, dilute sodium hydroxide?

    • Cl2 + 2OH^- -> 2Cl^- + O2 + H2
    • Cl2 + 2H^+ -> 2Cl^- + 2H2
    • Cl2 + OH^- -> Cl^- + HClO
    • Cl2 + 2OH^- -> Cl^- + ClO^- + H2O

  17. Which ion is the active disinfectant when chlorine dissolves in water to treat drinking water?

    • The hydroxide ion, OH^-
    • The chlorate(I) ion, ClO^-
    • The chloride ion, Cl^-
    • The sodium ion, Na^+

  18. What is the oxidation state of chlorine in sodium chlorate(I), NaClO?

    • +1
    • -1
    • 0
    • +5

  19. Why does a solution of sodium chlorate(I) bleach coloured materials?

    • The solution is acidic, which dissolves the dyes away from the fabric
    • The sodium ion reacts with the dye to form a colourless salt
    • The chlorate(I) ion is a strong reducing agent that removes colour from materials
    • The chlorate(I) ion is a strong oxidising agent that destroys the coloured compounds

  20. What is the balanced equation for the reaction of chlorine with water that forms chloride ions and oxygen?

    • 2Cl2 + 2H2O -> 4HCl + O2
    • Cl2 + 2H2O -> HCl + HClO2
    • Cl2 + H2O -> HCl + O2
    • 2Cl2 + H2O -> 2HCl + O2

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