Lesson 5.2.3

5.2.3 Redox and electrode potentials Quiz: OCR Chemistry, Unit 4

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

In partnership with Revision Ninja

Lesson 5.2.3, Redox and electrode potentials: 20 multiple choice questions for the OCR Chemistry (H432), Unit 4: Physical chemistry and transition elements, written with Revision Ninja.

Host it live on the board and students join with a game code on their own devices, or revise alone with Free Play. The answers are revealed in the game.

Host this setFree Play

The 20 questions

  1. In a redox reaction, what does an oxidising agent do to electrons?

    • Donates electrons
    • Accepts electrons
    • Releases protons
    • Shares electrons

  2. What is the oxidation number of manganese in the permanganate ion, MnO4-?

    • +5
    • +2
    • +4
    • +7

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

    • +12
    • +7
    • +6
    • +3

  4. What is the standard electrode potential of the standard hydrogen electrode by definition?

    • +0.34 V
    • 0.00 V
    • -0.76 V
    • +1.23 V

  5. Which expression gives the standard cell potential, E°cell, of an electrochemical cell?

    • E°negative - E°positive
    • E°positive - E°negative
    • E°negative / E°positive
    • E°positive + E°negative

  6. Standard electrode potentials are E(Cu2+/Cu) = +0.34 V and E(Zn2+/Zn) = -0.76 V. What is the standard cell potential for a Zn/Cu cell?

    • +1.10 V
    • -1.10 V
    • -0.42 V
    • +0.42 V

  7. How many electrons are gained per dichromate ion, Cr2O7²⁻, when reduced to Cr³⁺?

    • Seven electrons
    • Six electrons
    • Fourteen electrons
    • Three electrons

  8. In the reaction between iodine and thiosulfate, I2 + 2S2O3^2- -> 2I- + S4O6^2-, what is the mole ratio of I2 to S2O3^2- ions?

    • 2:1
    • 1:2
    • 1:4
    • 1:1

  9. In the redox titration of Fe2+ with MnO4- in acid, the balanced equation is MnO4- + 5Fe2+ + 8H+ -> Mn2+ + 5Fe3+ + 4H2O. What is the mole ratio of MnO4- to Fe2+?

    • 8:1
    • 1:5
    • 1:1
    • 5:1

  10. A 25.0 cm^3 sample of 0.0200 mol dm^-3 MnO4- reacts exactly with 25.0 cm^3 of Fe2+ solution in acid. What is the concentration of Fe2+?

    • 0.500 mol dm^-3
    • 0.100 mol dm^-3
    • 0.0200 mol dm^-3
    • 0.0040 mol dm^-3

  11. What is the oxidation number of sulfur, on average, in the thiosulfate ion, S2O3^2-?

    • -2
    • +6
    • +2
    • +4

  12. What is the standard electrode potential of the Cu2+/Cu half-cell?

    • +0.34 V
    • +1.23 V
    • -0.76 V
    • +0.77 V

  13. What kinetic factor can prevent a thermodynamically feasible redox reaction from occurring?

    • Low activation energy
    • High activation energy
    • Negative cell potential
    • Positive cell potential

  14. The electrode potential E(Cu2+/Cu+) = +0.15 V and E(Cu+/Cu) = +0.52 V. What is the cell potential for the disproportionation 2Cu+ -> Cu2+ + Cu?

    • +0.67 V
    • +0.15 V
    • -0.37 V
    • +0.37 V

  15. E(Fe3+/Fe2+) = +0.77 V and E(I2/I-) = +0.54 V. What is the standard cell potential for 2Fe3+ + 2I- -> 2Fe2+ + I2, and is the reaction feasible?

    • -0.23 V, not feasible
    • +0.23 V, feasible
    • +1.31 V, not feasible
    • +0.23 V, not feasible

  16. What reaction occurs at the negative electrode of a hydrogen fuel cell?

    • Reduction of oxygen
    • Oxidation of hydrogen
    • Reduction of hydrogen
    • Oxidation of oxygen

  17. What form of energy is directly generated by a hydrogen-oxygen fuel cell?

    • Thermal energy
    • Electrical energy
    • Nuclear energy
    • Light energy

  18. In the reaction Zn + Cu2+ -> Zn2+ + Cu, which species is the reducing agent?

    • Zn2+
    • Zn
    • Cu
    • Cu2+

  19. What is the oxidation number of nitrogen in the nitrite ion, NO2-?

    • +5
    • -3
    • +3
    • +1

  20. In a disproportionation reaction, what happens to the reacting element?

    • Oxidised and reduced
    • Neutralised
    • Only reduced
    • Only oxidised

All OCR Chemistry quizzes