Lesson 5.4.3.5

5.4.3.5 Representation of reactions at electrodes as half equations (HT only) Quiz: AQA Combined Science, Unit 11

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 5.4.3.5, Representation of reactions at electrodes as half equations (HT only): 20 multiple choice questions for the AQA GCSE Combined Science (8464), Unit 11: Chemical changes, written with Revision Ninja.

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The 20 questions

  1. What type of reaction occurs when positive ions gain electrons at the cathode?

    • Reduction
    • Neutralisation
    • Combustion
    • Oxidation

  2. What type of reaction occurs when negative ions lose electrons at the anode?

    • Thermal decomposition
    • Reduction
    • Displacement
    • Oxidation

  3. Which half equation shows hydrogen forming at the cathode?

    • H2 -> 2H+ + 2e-
    • 2H+ + e- -> H2
    • 2H+ -> H2 + 2e-
    • 2H+ + 2e- -> H2

  4. Which half equation shows the reaction at the anode when hydroxide ions are discharged?

    • 4OH- -> O2 + 2H2O + 4e-
    • O2 + 2H2O + 4e- -> 4OH-
    • 2OH- -> O2 + 2H+
    • 4OH- + 4e- -> O2 + 2H2O

  5. Which half equation shows a reduction reaction?

    • 4OH- -> O2 + 2H2O + 4e-
    • 2Cl- -> Cl2 + 2e-
    • Cu -> Cu2+ + 2e-
    • 2H+ + 2e- -> H2

  6. Which half equation represents the oxidation of chloride ions?

    • Cu2+ + 2e- -> Cu
    • Cl2 + 2e- -> 2Cl-
    • 2H+ + 2e- -> H2
    • 2Cl- -> Cl2 + 2e-

  7. Which half equation is correctly balanced for copper ions being reduced?

    • Cu2+ + 2e- -> Cu
    • Cu2+ + 2e- -> Cu2
    • Cu2+ -> Cu + 2e-
    • Cu2+ + e- -> Cu

  8. Which half equation is balanced for sodium ions being reduced?

    • Na+ + e- -> Na
    • Na -> Na+ + 2e-
    • Na+ + 2e- -> Na
    • Na+ -> Na + e-

  9. In the half equation 4OH- -> O2 + 2H2O + 4e-, how many electrons are released per O2 formed?

    • 4
    • 6
    • 1
    • 2

  10. What must half equations be balanced for besides atoms?

    • Temperature
    • Volume
    • Charge
    • Mass

  11. Which half equation shows aluminium being extracted at the cathode?

    • Al3+ + e- -> Al
    • 2O2- -> O2 + 4e-
    • Al3+ + 3e- -> Al
    • Al -> Al3+ + 3e-

  12. Which half equation shows oxide ions being oxidised at the anode in aluminium extraction?

    • 2O2- + 4e- -> O2
    • 2O2- -> O2 + 4e-
    • O2- + 2e- -> O
    • O2 + 4e- -> 2O2-

  13. Which electrode is associated with oxidation during electrolysis?

    • Salt bridge
    • Anode
    • Cathode
    • Electrolyte

  14. How many moles of electrons are gained when 1 mol of Cu2+ is reduced to copper?

    • 2 mol
    • 4 mol
    • 3 mol
    • 1 mol

  15. Which species is oxidised at the anode during electrolysis of molten lead bromide?

    • Bromide ions
    • Lead atoms
    • Bromine atoms
    • Lead ions

  16. What is the product of the reduction half equation 2H+ + 2e- -> H2?

    • Oxygen gas
    • Hydrogen gas
    • Hydroxide ions
    • Water

  17. Electrolysis needs 0.2 mol of electrons to discharge 0.2 mol of H+ ions as in 2H+ + 2e- -> H2. How many moles of electrons are needed for 0.2 mol of H+ ions?

    • 0.1 mol
    • 0.2 mol
    • 0.05 mol
    • 0.4 mol

  18. How many moles of H2 are formed when 0.4 mol of electrons is passed through dilute acid?

    • 0.8 mol
    • 0.1 mol
    • 0.4 mol
    • 0.2 mol

  19. What type of chemical reaction is represented by the half equation 4OH- - 4e- -> O2 + 2H2O?

    • Neutralisation
    • Reduction
    • Oxidation
    • Combustion

  20. Combining the cathode and anode half equations for electrolysis of water gives which overall equation?

    • H2O -> H2 + O2
    • 2H2 + O2 -> 2H2O
    • 2H2O -> 2H2 + O2
    • 2H2O -> H2 + O2

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