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Redox: OCR A‑Level Chemistry B questions

Every OCR A-Level Chemistry B exam question on DM Redox (specification points DM(c)–(f)), 2016–2025, with its mark scheme and examiner’s report.

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2,049 questions

  1. Q35(a)(ii)

    June 2025 · Paper 1

    2 marksDM Redox
    The whole paper ↗
    June 2025 Paper 1, question 35(a)(ii): Write a balanced ionic equation for the reaction. [2]

  2. Q5(b)(i)

    June 2025 · Paper 2

    2 marksDM Redox
    The whole paper ↗
    June 2025 Paper 2, question 5(b)(i): When the VRFB is delivering a current, V(V) is reduced to V(IV) and V(II) is oxidised to V(III). Write the ionic equation and give the E o cell for the overall

  3. Q5(b)(ii)

    June 2025 · Paper 2

    2 marksDM Redox
    The whole paper ↗
    June 2025 Paper 2, question 5(b)(ii): A student sets up a cell to measure the E o cell for VO2+/ V3+ against Zn2+ / Zn at 298 K. Here is a diagram of the student’s cell. V zinc rod vanadium rod Zn2+

  4. Q5(b)(iii)

    June 2025 · Paper 2

    4 marksDM Redox
    Mark scheme (PDF)
    The whole paper ↗
    June 2025 Paper 2, question 5(b)(iii): A student has powdered samples of the metals (silver, tin and zinc) shown in Table 5.1, and an +(aq). acidic solution of VO2 The student wants to obtain a solut

  5. Q5(c)(i)

    June 2025 · Paper 2

    2 marksDM Redox
    The whole paper ↗
    June 2025 Paper 2, question 5(c)(i): From the article, give two advantages of Li-ion batteries over VRFBs as batteries for electric vehicles. Advantage 1 Advantage 2 [2]

  6. Q5(c)(ii)

    June 2025 · Paper 2

    2 marksDM Redox
    The whole paper ↗
    June 2025 Paper 2, question 5(c)(ii): From the article, give two advantages of VRFBs over Li-ion batteries for large-scale use in storing energy from an array of solar cells. Advantage 1 Advantage 2

  7. Q5(d)

    June 2025 · Paper 2

    1 markDM Redox
    The whole paper ↗
    June 2025 Paper 2, question 5(d): Both types of battery have a separator in the middle. Give the formulae of the particles that pass through the separators in each battery when they are in use.

  8. Q4(a)

    June 2025 · Paper 3

    2 marksDM Redox
    The whole paper ↗
    June 2025 Paper 3, question 4(a): In the paperclip solution, IO4 – ions. IO3 The oxidation and reduction half equations for this reaction are: – + 2H+ + 2e– – + H2O IO4 IO3 Mn2+ + 4H2O – + 8H+ +

  9. Q5(b)(iii)

    June 2024 · Paper 2

    3 marksDM Redox
    The whole paper ↗
    June 2024 Paper 2, question 5(b)(iii): Write two half-equations to show how H2O2 can either act as an oxidising agent or a reducing agent ‘depending on the company it keeps’. Oxidising agent: Reducin

  10. Q1(a)(i)

    June 2024 · Paper 3

    1 markDM Redox
    The whole paper ↗
    June 2024 Paper 3, question 1(a)(i): Name the electrode against which these values are measured. [1]

  11. Q1(a)(ii)

    June 2024 · Paper 3

    2 marksDM Redox
    The whole paper ↗
    June 2024 Paper 3, question 1(a)(ii): What are the standard conditions at which these standard electrode potentials are measured? [2]

  12. Q1(b)(i)

    June 2024 · Paper 3

    2 marksDM Redox
    The whole paper ↗
    June 2024 Paper 3, question 1(b)(i): Some students set up the cell below. The cell consists of a copper/copper ion half-cell and a lead/lead ion half-cell. The left-hand electrode is negative. – +

  13. Q1(b)(ii)

    June 2024 · Paper 3

    1 markDM Redox
    The whole paper ↗
    June 2024 Paper 3, question 1(b)(ii): Suggest how the students make the salt bridge. [1]

  14. Q1(b)(iii)

    June 2024 · Paper 3

    1 markDM Redox
    The whole paper ↗
    June 2024 Paper 3, question 1(b)(iii): Use Table 1.1 to calculate E o for the cell. E o cell = V [1]

  15. Q1(c)(i)

    June 2024 · Paper 3

    3 marksDM Redox
    The whole paper ↗
    June 2024 Paper 3, question 1(c)(i): Use Table 1.1 to write ion-electron half equations for the reactions happening at the negative and positive electrodes. Then write the equation for the overall

  16. Q1(c)(ii)

    June 2024 · Paper 3

    1 markDM Redox
    The whole paper ↗
    June 2024 Paper 3, question 1(c)(ii): Suggest the purpose of the porous separator shown in the diagram. [1]

  17. Q34(a)(i)

    June 2023 · Paper 1

    3 marksDM Redox
    The whole paper ↗
    June 2023 Paper 1, question 34(a)(i): Complete the labelled diagram to show the student’s cell. V Zn(s) Zn2+(aq) (1.0 mol dm–3) [3]

  18. Q34(a)(ii)

    June 2023 · Paper 1

    1 markDM Redox
    The whole paper ↗
    June 2023 Paper 1, question 34(a)(ii): Use the data in Table 34.1 to calculate E o cell for the student’s electrochemical cell. E o cell = V [1]

  19. Q34(a)(iii)

    June 2023 · Paper 1

    2 marksDM Redox
    The whole paper ↗
    June 2023 Paper 1, question 34(a)(iii): State the types of particle that cause the transfer of charge through the wire and the solutions. The wire The solutions [2]

  20. Q34(b)

    June 2023 · Paper 1

    3 marksDM Redox
    The whole paper ↗
    June 2023 Paper 1, question 34(b): Standard electrode potentials can be used to explain how some metals protect iron from rusting. A thin coating of zinc on the surface of iron will provide prote
All 58 questions on Redox, as a list
  1. June 2025, Paper 1, Q35(a)(ii) (2 marks): Write a balanced ionic equation for the reaction. [2]
  2. June 2025, Paper 2, Q5(b)(i) (2 marks): When the VRFB is delivering a current, V(V) is reduced to V(IV) and V(II) is oxidised to V(III). Write the ionic equation and give the E o cell for the overall
  3. June 2025, Paper 2, Q5(b)(ii) (2 marks): A student sets up a cell to measure the E o cell for VO2+/ V3+ against Zn2+ / Zn at 298 K. Here is a diagram of the student’s cell. V zinc rod vanadium rod Zn2+
  4. June 2025, Paper 2, Q5(b)(iii) (4 marks): A student has powdered samples of the metals (silver, tin and zinc) shown in Table 5.1, and an +(aq). acidic solution of VO2 The student wants to obtain a solut
  5. June 2025, Paper 2, Q5(c)(i) (2 marks): From the article, give two advantages of Li-ion batteries over VRFBs as batteries for electric vehicles. Advantage 1 Advantage 2 [2]
  6. June 2025, Paper 2, Q5(c)(ii) (2 marks): From the article, give two advantages of VRFBs over Li-ion batteries for large-scale use in storing energy from an array of solar cells. Advantage 1 Advantage 2
  7. June 2025, Paper 2, Q5(d) (1 mark): Both types of battery have a separator in the middle. Give the formulae of the particles that pass through the separators in each battery when they are in use.
  8. June 2025, Paper 3, Q4(a) (2 marks): In the paperclip solution, IO4 – ions. IO3 The oxidation and reduction half equations for this reaction are: – + 2H+ + 2e– – + H2O IO4 IO3 Mn2+ + 4H2O – + 8H+ +
  9. June 2024, Paper 2, Q5(b)(iii) (3 marks): Write two half-equations to show how H2O2 can either act as an oxidising agent or a reducing agent ‘depending on the company it keeps’. Oxidising agent: Reducin
  10. June 2024, Paper 3, Q1(a)(i) (1 mark): Name the electrode against which these values are measured. [1]
  11. June 2024, Paper 3, Q1(a)(ii) (2 marks): What are the standard conditions at which these standard electrode potentials are measured? [2]
  12. June 2024, Paper 3, Q1(b)(i) (2 marks): Some students set up the cell below. The cell consists of a copper/copper ion half-cell and a lead/lead ion half-cell. The left-hand electrode is negative. – +
  13. June 2024, Paper 3, Q1(b)(ii) (1 mark): Suggest how the students make the salt bridge. [1]
  14. June 2024, Paper 3, Q1(b)(iii) (1 mark): Use Table 1.1 to calculate E o for the cell. E o cell = V [1]
  15. June 2024, Paper 3, Q1(c)(i) (3 marks): Use Table 1.1 to write ion-electron half equations for the reactions happening at the negative and positive electrodes. Then write the equation for the overall
  16. June 2024, Paper 3, Q1(c)(ii) (1 mark): Suggest the purpose of the porous separator shown in the diagram. [1]
  17. June 2023, Paper 1, Q34(a)(i) (3 marks): Complete the labelled diagram to show the student’s cell. V Zn(s) Zn2+(aq) (1.0 mol dm–3) [3]
  18. June 2023, Paper 1, Q34(a)(ii) (1 mark): Use the data in Table 34.1 to calculate E o cell for the student’s electrochemical cell. E o cell = V [1]
  19. June 2023, Paper 1, Q34(a)(iii) (2 marks): State the types of particle that cause the transfer of charge through the wire and the solutions. The wire The solutions [2]
  20. June 2023, Paper 1, Q34(b) (3 marks): Standard electrode potentials can be used to explain how some metals protect iron from rusting. A thin coating of zinc on the surface of iron will provide prote
  21. June 2023, Paper 1, Q34(d) (2 marks): A student carries out the analysis described in part (c) but uses hydrochloric acid instead of sulfuric acid to dissolve the sample of the alloy. Using the data
  22. June 2022, Paper 1, Q26 (1 mark): Manganate(VII) ions react with sulfate(IV) ions as shown in the unbalanced equation below. –(aq) + SO3 2–(aq) + H+(aq) Mn2+(aq) + SO4 2–(aq) + H2O(l) MnO4 2–(aq
  23. June 2022, Paper 1, Q29 (1 mark): Two half-cell equations are shown with their standard electrode potentials. E o = – 0.26 V V3+(aq) + e– V2+(aq) E o = +0.34 V VO2+(aq) + 2H+(aq) + e– V3+(aq) +
  24. June 2022, Paper 3, Q3(a)(i) (2 marks): Write half-equations for the reactions that take place in each half-cell. Show state symbols. oxidation reaction: reduction reaction: [2]
  25. June 2022, Paper 3, Q3(a)(ii) (2 marks): Explain the purpose of the salt bridge. [2]
  26. June 2022, Paper 3, Q3(a)(iii) (1 mark): Calculate E o cell for the copper/zinc cell in Fig. 3.1. E o cell = V [1]
  27. June 2022, Paper 3, Q3(b)(i) (1 mark): Metallic silver is added to aqueous iron(II) sulfate. [1]
  28. June 2022, Paper 3, Q3(b)(ii) (2 marks): Aqueous potassium chloride is added to acidified potassium manganate(VII) solution. [2]
  29. June 2022, Paper 3, Q3(c)(i) (2 marks): Explain how Equation 3.1 shows that E = E o under standard conditions. [2]
  30. June 2022, Paper 3, Q3(c)(ii) (2 marks): Calculate the electrode potential of a Zn2+(aq) / Zn(s) half-cell when [Zn2+(aq)] = 0.20 mol dm–3. E = V [2] Standard electrode potential, Half reaction E o / V
  31. June 2022, Paper 3, Q3(d) (4 marks): The rusting of iron is an electrochemical process. A solution of ‘ferroxyl’ indicator can be used to investigate the reactions taking place in rusting. This ind
  32. November 2021, Paper 1, Q31(b)(ii) (1 mark): Use the oxidation states to construct an equation for the oxidation of ammonium ions using atmospheric oxygen. An acidic solution containing nitrate ions is for
  33. November 2021, Paper 2, Q2(a)(i) (2 marks): Complete half-equation 3 in Table 2.1 by writing numbers on the dotted lines. [2]
  34. November 2021, Paper 2, Q2(b)(i) (3 marks): Complete the diagram of their apparatus. Indicate how standard conditions are obtained. [3]
  35. November 2021, Paper 2, Q2(b)(ii) (1 mark): Use the data in Table 2.1 to calculate the E o cell value for the cell in (b)(i). E o cell = V [1]
  36. November 2021, Paper 2, Q2(c) (4 marks): Zinc blocks are often fixed to the bottom of steel ships to stop the ships rusting in sea water. A student compares this process with the cell in part (b)(i). T
  37. November 2020, Paper 1, Q14 (1 mark): X is an iron nail partially covered in zinc. Y is a plain iron nail. iron nail X iron nail Y covering of zinc wire water water Which statement about rusting is
  38. November 2020, Paper 2, Q2(a)(i) (2 marks): There is something missing from the diagram. State what it is and describe what it is made of. [2]
  39. November 2020, Paper 2, Q2(a)(ii) (2 marks): State two conditions necessary for the cell to measure electrode potentials under standard conditions. 1 2 [2]
  40. November 2020, Paper 2, Q2(b)(ii) (1 mark): State and explain which way electrons flow in the wire when the standard cell is delivering a current. [1]
  41. November 2020, Paper 2, Q2(c) (4 marks): Silver bromide, AgBr, is usually described as ‘insoluble’ but a small amount can dissolve in water. The students have a saturated solution of AgBr. This contain
  42. November 2020, Paper 2, Q2(d)(i) (2 marks): Write an equation for the reaction that occurs when the cell delivers a current. [2]
  43. November 2020, Paper 2, Q2(d)(ii) (2 marks): Draw a labelled diagram to show how the IO3 You do not need to give concentrations. [2]
  44. June 2019, Paper 2, Q3(b)(i) (2 marks): The forward reaction in equation 3.1 does not occur under standard conditions. Use data from Table 3.1 to explain why. [2]
  45. June 2019, Paper 2, Q3(b)(ii) (2 marks): Suggest why the forward reaction in equation 3.1 does occur in the presence of concentrated hydrochloric acid. [2]
  46. June 2019, Paper 2, Q3(c)(i) (4 marks): The student uses a Cu2+(aq)/Cu(s) half-cell to confirm the Eo of a Cl 2(aq)/Cl −(aq) half-cell. Complete and label the diagram of the apparatus the student woul
  47. June 2019, Paper 2, Q3(c)(ii) (1 mark): Give the value of Eo cell for the cell in (c)(i). Eo cell = V [1]
  48. June 2019, Paper 2, Q3(c)(iii) (1 mark): State where the electrons move and which way they are moving when the cell delivers a current. [1]
  49. June 2019, Paper 2, Q3(c)(iv) (1 mark): A standard hydrogen electrode is used to measure Eo values, such as those in Table 3.1. Give the half-cell reaction that occurs at a hydrogen electrode. Show st
  50. June 2019, Paper 2, Q3(c)(v) (2 marks): The E value for the copper electrode at 298 K varies with the concentration of copper ions. The equation for this is shown below. E = Eo + 0.0128 l n [Cu2+] Cal
  51. June 2018, Paper 1, Q35(c)(i) (2 marks): Give the half-equations for the processes occurring during the rusting. [2]
  52. June 2018, Paper 1, Q35(c)(ii) (1 mark): What are the formulae of the green and orange solids? Green solid Orange solid [1]
  53. June 2018, Paper 1, Q35(c)(iii) (1 mark): Suggest why rusting takes place faster in seawater than in rainwater. [1]
  54. June 2018, Paper 1, Q35(e) (2 marks): Use the electrode potentials in the table below to explain why only the nickel reacts. E ϴ / V Half reaction Ni2+(aq) + 2e– Ni(s) – 0.25 2H+(aq) + 2e– 0.00 H2(g
  55. June 2018, Paper 3, Q2(a)(i) (1 mark): Suggest one advantage and one disadvantage of using a calomel electrode over a standard hydrogen electrode. Advantage Disadvantage [1]
  56. June 2018, Paper 3, Q2(c) (6 marks): The use of a standard hydrogen electrode for measuring standard electrode potentials is often not practicable. The diagram below shows a calomel electrode. This
  57. June 2017, Paper 1, Q10 (1 mark): A student is given the electrode potentials below. Cu2+ + 2e– E ө = +0.34 V Cu Ag+ + e– E ө = +0.80 V Ag The student sets up a cell from the two half cells. Whi
  58. June 2017, Paper 1, Q28 (1 mark): Which statement(s) about rusting is/are correct? Rust contains Fe3+ ions. 1 2 Oxygen molecules are reduced during rusting. Fe3+ + 3e–. 3 The first step in rusti

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