Lesson 3.1.2

3.1.2 Oxidation, reduction and electron transfer Quiz: Pearson Edexcel Chemistry, Unit 3

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.1.2, Oxidation, reduction and electron transfer: 20 multiple choice questions for the Pearson Edexcel Chemistry (9CH0), Unit 3: Redox I, written with Revision Ninja.

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The 20 questions

  1. What does an oxidising agent do in a reaction?

    • It gains protons and is itself oxidised
    • It gains electrons and is itself reduced
    • It loses electrons and is itself oxidised
    • It loses electrons and is itself reduced

  2. What does a reducing agent do in a reaction?

    • It loses electrons and is itself oxidised
    • It gains electrons and is itself reduced
    • It loses protons and is itself reduced
    • It gains electrons and is itself oxidised

  3. In the reaction 2Mg + O2 -> 2MgO, which species is oxidised?

    • No species is oxidised
    • Magnesium oxide
    • Magnesium
    • Oxygen

  4. In the reaction 2Na + Cl2 -> 2NaCl, what is the oxidation number change of chlorine?

    • +1 to -1
    • -1 to 0
    • 0 to +1
    • 0 to -1

  5. Which species acts as the oxidising agent in 2Fe2+ + Cl2 -> 2Fe3+ + 2Cl-?

    • Chlorine, Cl2
    • Chloride ion, Cl-
    • Iron(II) ion, Fe2+
    • Iron(III) ion, Fe3+

  6. Why is the reaction of Cl2 with Br- an example of a redox reaction?

    • Chlorine and bromide exchange positions without any change in charge, so no electrons are actually transferred between them
    • Chlorine gains electrons and bromide loses electrons, so both oxidation numbers change
    • Neither species changes its oxidation number, because the reaction involves only a simple exchange of ions in solution
    • Only bromine changes its oxidation number in the reaction, while chlorine stays at zero throughout the process

  7. What is the oxidation number of sulfur in H2S?

    • 0
    • +2
    • -2
    • +6

  8. In the reaction Cu + 2Ag+ -> Cu2+ + 2Ag, what is the reducing agent?

    • Copper(II) ion, Cu2+
    • Copper, Cu
    • Silver ion, Ag+
    • Silver, Ag

  9. Which equation shows oxidation of iron?

    • Fe -> Fe2+ + 2e-
    • Fe2+ -> Fe3+ + e-
    • Fe3+ + e- -> Fe2+
    • Fe3+ + 3e- -> Fe

  10. Which species is reduced when permanganate is used in acidic solution?

    • Fe2+ to Fe3+
    • MnO4- to Mn2+
    • H2O to O2
    • Mn2+ to MnO4-

  11. In a redox reaction, which statement about electron transfer is correct?

    • The total number of electrons lost by the reducing agent equals the total number gained by the oxidising agent
    • Electrons are created during oxidation and destroyed during reduction, so the total number changes in every reaction
    • Oxidation involves the gain of protons from the solvent, which is why the oxidation number increases in the reaction
    • Only metals can be oxidised in a redox reaction, because non-metals always gain electrons and are reduced

  12. Why does a reduction always accompany an oxidation?

    • Electrons lost by one species must be gained by another species
    • Oxidation is always followed by a change in pH of the solution, which is what triggers reduction of the other species
    • Reduction occurs only when a gas is evolved from the reaction mixture, so oxidation must produce a gas first
    • Oxidation produces electrons that reduction then absorbs as heat, so the energy released is always balanced in the reaction

  13. In the reaction 2H+ + Mg -> Mg2+ + H2, what is the oxidation number change of hydrogen?

    • +1 to 0
    • +1 to -1
    • 0 to -1
    • 0 to +1

  14. Which species is oxidised in the reaction between iodide and chlorine?

    • Iodide ion, I-
    • Chlorine, Cl2
    • Chloride ion, Cl-
    • Iodine, I2

  15. Explain why the reaction of zinc with copper(II) sulfate is a redox reaction.

    • Zinc is oxidised from 0 to +2 and copper is reduced from +2 to 0, so electrons are transferred
    • Zinc and copper(II) sulfate exchange sulfate ions without any change in oxidation number, so no electrons are transferred
    • Copper(II) sulfate is oxidised while zinc stays neutral, because the sulfate ion carries the electrons away from zinc
    • Only the sulfate ion changes oxidation number during the reaction, while both the zinc and copper atoms remain unchanged

  16. Which statement about oxidising agents is correct?

    • A good oxidising agent is easily oxidised, losing electrons readily
    • An oxidising agent is always an element in Group 1
    • A good oxidising agent is easily reduced, gaining electrons readily
    • An oxidising agent gains protons to become reduced

  17. A reaction shows the oxidation number of iron changing from +2 to +3. Which statement is correct?

    • Iron has been oxidised and has lost one electron
    • Iron has gained two electrons, which is why its oxidation number rises by two units during the change
    • Iron has been reduced and gained one electron, which lowers its oxidation number from +3 back down to +2
    • Iron has lost two electrons and been reduced, which is why the oxidation number changes by a total of one

  18. Which species is acting as the reducing agent in 2Br- + Cl2 -> Br2 + 2Cl-?

    • Bromine, Br2
    • Chlorine, Cl2
    • Bromide ion, Br-
    • Chloride ion, Cl-

  19. Explain how oxidation number and electron transfer are related.

    • Oxidation numbers change only when protons are transferred between the species in the reaction mixture
    • A decrease in oxidation number corresponds to a loss of electrons, which is the reverse of the usual pattern
    • An increase in oxidation number corresponds to a loss of electrons, and a decrease corresponds to a gain of electrons
    • Oxidation number and electron transfer are unrelated concepts, so one cannot be used to predict the other at all

  20. Which reaction is a redox reaction in which hydrogen is oxidised?

    • H2 + Cl2 -> 2HCl, with hydrogen going from 0 to +1
    • NaOH + HCl -> NaCl + H2O, with no change in oxidation number
    • CaCO3 -> CaO + CO2, with carbon keeping the same oxidation number
    • 2HCl -> H2 + Cl2, with hydrogen going from +1 to 0

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