Lesson 3.1.7

3.1.7 Oxidation, reduction and redox equations Quiz: AQA Chemistry, Unit 1

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.1.7, Oxidation, reduction and redox equations: 20 multiple choice questions for the AQA Chemistry (7405), Unit 1: Physical chemistry, written with Revision Ninja.

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The 20 questions

  1. In redox chemistry, what is oxidation defined as?

    • Loss of protons by a species in every reaction
    • Gain of electrons by a species
    • Gain of positive charge by a species in every reaction
    • Loss of electrons by a species

  2. In redox chemistry, what is reduction defined as?

    • Loss of negative charge by a species in every reaction
    • Gain of hydrogen by a species in every reaction
    • Loss of electrons by a species
    • Gain of electrons by a species

  3. What is an oxidising agent?

    • A substance that always contains oxygen and is consumed in the reaction
    • An electron acceptor, which is itself reduced in the reaction
    • An electron donor, which is itself oxidised in the reaction
    • A species that is oxidised and loses protons to the solvent

  4. What is a reducing agent?

    • An electron donor, which is itself oxidised in the reaction
    • A species that is reduced and gains protons from the solvent
    • A substance that always contains hydrogen and is consumed in the reaction
    • An electron acceptor, which is itself reduced in the reaction

  5. What is the oxidation state of chromium in the dichromate ion, Cr2O7^2-?

    • +6
    • +7
    • +3
    • +12

  6. What is the oxidation state of manganese in the permanganate ion, MnO4^-?

    • +2
    • +5
    • +6
    • +7

  7. What is the oxidation state of sulfur in the sulfate ion, SO4^2-?

    • +4
    • +6
    • +2
    • -2

  8. What is the oxidation state of sulfur in hydrogen sulfide, H2S?

    • -2
    • +2
    • +6
    • 0

  9. What is the oxidation state of chlorine in the chlorate(I) ion, ClO^-?

    • +7
    • +1
    • +5
    • -1

  10. What is the oxidation state of nitrogen in the ammonium ion, NH4^+?

    • +5
    • -3
    • +3
    • -1

  11. What is the oxidation state of oxygen in hydrogen peroxide, H2O2?

    • +1
    • -2
    • 0
    • -1

  12. In the half-equation Fe^2+ -> Fe^3+ + e^-, what process occurs?

    • Reduction, because iron gains an electron
    • Oxidation, because iron gains a proton
    • Reduction, because iron loses an electron
    • Oxidation, because iron loses an electron

  13. In the half-equation MnO4^- + 8H^+ + 5e^- -> Mn^2+ + 4H2O, which process occurs?

    • Reduction, because manganese loses five electrons and its oxidation state falls from +7 to +2
    • Reduction, because manganese gains five electrons and its oxidation state falls from +7 to +2
    • Oxidation, because the hydrogen ions gain electrons from the manganese centre
    • Oxidation, because manganese loses five electrons and its oxidation state rises from +7 to +9

  14. Combining MnO4^- + 8H^+ + 5e^- -> Mn^2+ + 4H2O with Fe^2+ -> Fe^3+ + e^- gives an overall equation. How many moles of Fe^2+ react with one mole of MnO4^-?

    • 1
    • 5
    • 4
    • 8

  15. For the reduction half-equation Cr2O7^2- + 14H^+ + 6e^- -> 2Cr^3+ + 7H2O, how many electrons are transferred per dichromate ion?

    • 3
    • 14
    • 2
    • 6

  16. In the reaction Zn(s) + Cu^2+(aq) -> Zn^2+(aq) + Cu(s), which species is the oxidising agent?

    • Cu^2+, because it accepts electrons and is reduced
    • Zn^2+, because it donates electrons and is oxidised
    • Cu, because it donates electrons and is oxidised
    • Zn, because it accepts electrons and is reduced

  17. In the reaction Cl2 + 2OH^- -> Cl^- + ClO^- + H2O, what happens to chlorine?

    • It is both oxidised and reduced, as its oxidation state goes from 0 to -1 and to +1
    • It is only reduced, because its oxidation state falls from 0 to -1 in every product
    • It is neither oxidised nor reduced, because chlorine is a diatomic molecule
    • It is only oxidised, because its oxidation state rises from 0 to +1 in every product

  18. In the half-equation 2S2O3^2- -> S4O6^2- + 2e^-, what is the change in the average oxidation state of sulfur?

    • It falls from +2 to +1.5, so sulfur is reduced
    • It rises from +2 to +2.5, so sulfur is oxidised
    • It stays at +2, so sulfur is neither oxidised nor reduced
    • It rises from +2 to +6, so sulfur is oxidised

  19. Using the 1:5 ratio from the overall redox equation for MnO4^- and Fe^2+, how many moles of MnO4^- are needed to react completely with 0.0200 mol of Fe^2+?

    • 0.00400 mol
    • 0.0200 mol
    • 0.00100 mol
    • 0.100 mol

  20. Which species is oxidised in the reaction Mg(s) + 2HCl(aq) -> MgCl2(aq) + H2(g)?

    • Chlorine, which changes from oxidation state -1 to 0
    • Hydrogen, which changes from oxidation state +1 to 0
    • Magnesium, which changes from oxidation state 0 to +2
    • Hydrogen, which changes from oxidation state 0 to +1

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