Electrode potentials and cells: Edexcel International A Level Chemistry questions

Every Edexcel International A Level Chemistry exam question on Electrode potentials and cells (specification points 16.1–16.14), 2019–2025, with its mark scheme and examiner’s report.

All 96 questions on Electrode potentials and cells, as a list

June 2025, Unit 5, Q1 (1 mark): Which reaction is thermodynamically feasible under standard conditions? Use your Data Booklet. 3+ → Ag + + V 2+ A Ag + V + + V 3+ → Cu 2+ + V 2+ B Cu 2+ + V 3+
June 2025, Unit 5, Q14(a) (2 marks): State the name and purpose of part X. (2)
June 2025, Unit 5, Q14(b) (2 marks): Draw a cell diagram for this system. (2)
June 2025, Unit 5, Q14(c) (2 marks): The electrode system for the titanium ions is shown. 3+(aq) + e –  Ti 2+(aq) Ti Ed = −0.37 V Calculate the Ed cell value. Use your Data Booklet. (2)
June 2025, Unit 5, Q14(d) (3 marks): State the changes, if any, that would occur to the cell emf, the electrodes and the ion concentrations when current flows for several hours in this cell. (3)
June 2025 (A), Unit 5, Q1(a) (1 mark): Which electrodes are used for this cell? (1) Electrode 1 Electrode 2 A iron zinc B platinum platinum C zinc iron zinc platinum D
June 2025 (A), Unit 5, Q1(b) (1 mark): The solution for the right‑hand half‑cell is prepared by adding suitable amounts of iron(II) sulfate and iron(III) sulfate to distilled water to make 1.00 dm3 o
June 2025 (A), Unit 5, Q4 (1 mark): The standard emf, Ed cell , of a reaction is positive. Which must be correct? A the entropy change of the system, ΔS d system , is positive B the entropy change
January 2025, Unit 5, Q8 (1 mark): Which is correct about standard electrode potentials? cell is proportional to ln K and ln ΔStotal A E d cell is proportional to ln K and ΔStotal B E d cell is p
January 2025, Unit 5, Q18(a)(i) (4 marks): Identify, by name or formula, the substances needed in the salt bridge and the right‑hand half‑cell. Include concentrations where appropriate. (4) A Salt bridge
January 2025, Unit 5, Q18(a)(ii) (1 mark): State why a salt bridge is used rather than a wire. (1)
January 2025, Unit 5, Q18(b) (2 marks): Write an equation for the reaction that would take place if current was allowed to flow through the circuit. State symbols are not required. (2)
January 2025, Unit 5, Q18(c) (2 marks): Under standard conditions, the E d cell for this reaction is +1.53 V. State what would happen to this value, if anything, when the Zn2+ solution in the half‑cel
January 2025, Unit 5, Q20(a)(i) (2 marks): Write the equation for Reaction 1. Use the half‑equations from page 10 of your Data Booklet. State symbols are not required. (2)
January 2025, Unit 5, Q20(a)(ii) (2 marks): In Reaction 2, Cr2O7 2– reacts with a metal, M, in acid conditions forming Cr3+ and M2+. 2–. Identify a possible metal, M, calculating E d cell for its reaction
October 2024, Unit 5, Q17(a) (6 marks): Describe how you would carry out an experiment to determine the standard electrode potential of the electrode system shown. Co2+(aq) + 2e−  Co(s) Assume that y
October 2024, Unit 5, Q17(b) (3 marks): Acidified potassium dichromate(VI) is an oxidising agent. The acid commonly used is sulfuric acid. Explain, using reference to the electrode potentials shown, w
October 2024, Unit 5, Q17(c) (1 mark): The cell diagram for an electrochemical cell is shown. Ag(s) | Ag+(aq) || [VO2 +(aq) + 2H+(aq)], [VO2+(aq) + H2O(l)] | Pt(s) Write the reduction half-equation f
October 2024, Unit 5, Q17(d)(iii) (1 mark): The reduction half-cell in the DMFC has a standard electrode potential E = +1.23 V . When the solution concentration changes, the electrode potential changes so
October 2024, Unit 6, Q1(b) (2 marks): The student added a sample of a pale‑brown, aqueous solution of Q to a colourless aqueous solution of P. The student observed the formation of a darker brown so
June 2024, Unit 5, Q4 (1 mark): The emf, E d cell , of the cell made up of the copper and magnesium half‑cells is measured under standard conditions. The voltmeter used has a measurement uncer
June 2024, Unit 5, Q5 (1 mark): Which is the diagram for the cell made up of the nickel and zinc half‑cells that gives a positive value for E d cell? Use your Data Booklet. A Zn(s) | Zn2+(aq)
June 2024, Unit 5, Q6 (1 mark): Which graph shows the relationship between E d cell plotted on the x‑axis and ΔStotal on the y‑axis for any electrochemical system? A B C D
June 2024, Unit 5, Q14(a)(i) (1 mark): Name the type of the forward reaction that is shown in the right‑hand electrode systems in the Data Booklet. (1)
June 2024, Unit 5, Q14(a)(ii) (1 mark): Name the series formed when the right‑hand electrode systems are placed in order, most negative first. (1)
June 2024, Unit 5, Q14(b)(i) (2 marks): Identify X and Y. (2) X: Y:
June 2024, Unit 5, Q14(b)(ii) (2 marks): Give two reasons why the initial reading on the voltmeter may differ from the stated value given in the Data Booklet. (2)
June 2024, Unit 5, Q14(b)(iii) (2 marks): The voltmeter is removed and the cell is allowed to run for one hour. Explain the changes that would occur in the right‑hand half‑cell during this time. (2)
June 2024, Unit 5, Q14(c)(i) (4 marks): Explain, by calculating E d cell values, why Fe(II) is used to reduce Cr(VI) to Cr(III) but zinc is used to reduce Cr(VI) to Cr(II). (4) Numbers chosen of the r
June 2024, Unit 5, Q14(c)(ii) (1 mark): State the essential condition required for these reactions to occur. (1)
January 2024, Unit 5, Q1(a) (1 mark): Which electrodes are used for this cell? (1) electrode 1 electrode 2 A platinum platinum B platinum chromium C zinc chromium D zinc platinum
January 2024, Unit 5, Q1(b) (1 mark): A student wishes to measure the standard cell potential, Ecell , of this cell. The right‑hand cell requires Cr3+ and Cr2+ ions. What mass of Cr2(SO4)3·18H2O mus
January 2024, Unit 5, Q1(c) (1 mark): What can be deduced from the fact that, for this reaction, Ecell is positive? (1) A ΔStotal and ln K are positive B ΔStotal and ln K are negative C ΔStotal is p
January 2024, Unit 5, Q4 (1 mark): Which sequence shows the ions in order of increasing strength as a reducing agent? Refer to your Data Booklet. A V2+ < Fe2+ < Cr2+ B Cr2+ < Fe2+ < V2+ C Cr2+ <
January 2024, Unit 5, Q16(a)(i) (1 mark): Justify the assignment of the oxidation state of +5 to manganese in H3MnO4 using oxidation numbers. (1)
January 2024, Unit 5, Q16(a)(ii) (2 marks): Write an equation for the reaction of H3MnO4 in acidic solution to give ions containing manganese(VI) and manganese(IV). Use the Latimer diagram to obtain the f
January 2024, Unit 5, Q16(a)(iii) (2 marks): Deduce whether or not this disproportionation reaction is thermodynamically feasible by calculating E for the reaction. (2)
October 2023, Unit 5, Q7 (1 mark): E cell is directly proportional to A ∆ rH and ln K B ∆ rH and ln RT C ∆Stotal and ln K D ∆Stotal and ln RT Use this space for any rough working. Anything you wr
October 2023, Unit 5, Q8 (1 mark): Standard electrode potentials can also be given an alternative name. The electrochemical series lists standard electrode potentials in order. Which of these is
October 2023, Unit 5, Q10 (1 mark): The emf, E cell , of a cell is +0.57 V. The numerical values of the standard electrode potentials of the two half-cells joined in this cell are 0.17 V and 0.40
October 2023, Unit 5, Q11 (1 mark): An electrochemical cell is set up: • a half-cell is made from a piece of zinc and a solution of zinc chloride, ZnCl2 a second half-cell is made from a piece of
October 2023, Unit 5, Q18(a) (5 marks): Draw a labelled diagram of the apparatus you would use to measure the standard electrode potential of a Cu2+(aq) | Cu(s) electrode with a standard hydrogen elec
October 2023, Unit 5, Q18(b)(i) (3 marks): Explain, in terms of electrode potentials, why acidified dichromate(VI) ions react with concentrated hydrochloric acid to form chlorine, even though E cell = −
October 2023, Unit 5, Q18(b)(ii) (2 marks): Write the cell diagram, using the conventional representation of half-cells, for the reaction to produce chlorine. (2)
June 2023, Unit 5, Q1 (1 mark): The equation for a redox reaction is shown. 2V2+(aq) + Cu2+(aq) → 2V3+(aq) + Cu(s) What is the cell diagram for this reaction? A V(s) | V3+(aq), V2+(aq) | | Cu(
June 2023, Unit 5, Q2 (1 mark): Some standard electrode potentials are shown. Right-hand electrode system E / V Mg2+ + 2e–  Mg –2.37 –2.33 Ce3+ + 3e–  Ce Mn2+ + 2e–  Mn –1.19 Mn3+ + e–  Mn
June 2023, Unit 5, Q3 (1 mark): In a chemical reaction, Ecell is directly proportional to A Kc B rH C Ssystem D Stotal
June 2023, Unit 5, Q4 (1 mark): For the reaction shown, Ecell = +0.89 V. 4V3+(aq) + O2(g) + 2H2O(l) → 4VO2+(aq) + 4H+(aq) Which statement can be deduced from this information only? A the react
June 2023, Unit 5, Q21(d)(i) (1 mark): Suggest why KCl crystals are needed in the outer tube of the electrode. (1)
June 2023, Unit 5, Q21(d)(ii) (1 mark): A calomel electrode was used to measure the standard electrode potential of the Sn2+(aq) | Sn(s) half‑cell. – + V Sn(s) 1.0 mol dm–3 Sn2+(aq) The reading on the
June 2023, Unit 5, Q21(d)(iii) (1 mark): Write the overall equation for the cell reaction. (1)
June 2023, Unit 5, Q21(d)(iv) (3 marks): Add labels to complete the diagram of a standard hydrogen electrode. Include details of any essential conditions. (3) V salt bridge KNO3(aq)
June 2023, Unit 5, Q21(d)(v) (1 mark): Suggest one advantage of using a calomel electrode, in place of a standard hydrogen electrode, when measuring a cell potential. (1)
January 2023, Unit 5, Q8 (1 mark): The cell diagram for an electrochemical cell is shown. Pt(s) | Fe2+(aq), Fe3+(aq) || Br2(aq), 2Br–(aq) | Pt(s) Ecell = +0.32 V What are the half-equations for t
January 2023, Unit 5, Q20(f)(i) (2 marks): Write the half-equations for the reactions at the anode and the cathode. (2) anode half-equation: cathode half-equation:
January 2023, Unit 5, Q20(f)(ii) (1 mark): The standard electrode potential for the Zn / ZnO half-cell is –1.28 V. Calculate the standard electrode potential for the MnO2 / Mn2O3 half-cell. (1)
October 2022, Unit 5, Q2 (1 mark): What is the pressure of hydrogen gas used in the standard hydrogen electrode? A 1 Pa B 100 Pa C 1 000 Pa D 100 000 Pa Use this space for any rough working. Anyt
October 2022, Unit 5, Q3(a) (1 mark): What materials will be used for the electrodes in this cell? (1) 2− , Cr3+ TiO2+ , Ti3+ Cr2O7 A chromium titanium B chromium platinum C platinum titanium D plat
October 2022, Unit 5, Q3(b) (1 mark): The reaction between Cr2O7 2− , Cr3+ electrode system is +1.33 V. The standard electrode potential for the Cr2O7 What is the standard electrode potential for th
October 2022, Unit 5, Q4 (1 mark): The possibility of a reaction between potassium dichromate(VI) and hydrochloric acid may be assessed using standard electrode potentials but also depends on the
June 2022, Unit 5, Q17(a)(ii) (3 marks): Explain, by considering both thermodynamic and kinetic factors, why HSO3 reduces Cu2+ to Cu+ but does not then reduce Cu+ to Cu. Use the data in the table. (3)
June 2022, Unit 5, Q17(d)(i) (3 marks): Draw a labelled diagram of the apparatus used to measure the emf of a cell with copper and zinc electrodes under standard conditions. (3)
June 2022, Unit 5, Q17(d)(ii) (3 marks): The Nernst equation describes the relationship between the concentration of metal ions in a half-cell and its electrode potential. E = E + 0 0260 . × ln [ion] z
June 2022, Unit 6, Q3(b)(i) (2 marks): Use the electrode potential data to explain why the redox reaction might not be expected to be feasible. (2)
June 2022, Unit 6, Q3(b)(ii) (2 marks): Explain why the redox reaction does, in fact, take place. (2)
January 2022, Unit 5, Q3(a) (1 mark): Which silver compound could be used as the electrolyte in the left‑hand half‑cell? (1) A silver nitrate B silver hydroxide C silver chloride D silver carbonate
January 2022, Unit 5, Q3(b) (1 mark): The electrolyte in the right‑hand half‑cell is prepared using equal volumes of (1) A 1 mol dm−3 acidified VO2 +(aq) and 1 mol dm−3 acidified VO2+(aq) B 2 mol dm
January 2022, Unit 5, Q3(c) (1 mark): Which is the equation for the overall cell reaction under standard conditions? (1) A VO2+(aq) + Ag+(aq) + H2O(l) → VO2 +(aq) + Ag(s) + 2H+(aq) → VO2+(aq) + Ag+(
January 2022, Unit 5, Q3(d) (1 mark): Which is the value of Ecell in volts? (1) A −1.80 B −0.20 C +0.20 D +1.80
January 2022, Unit 5, Q3(e) (1 mark): Which is the cell diagram for this cell, using the conventional representation of half‑cells? (1) A Ag(s) | Ag+(aq) | | [VO2 +(aq) + 2H+(aq)] | [VO2+(aq) + H2O(
January 2022, Unit 5, Q10(c) (1 mark): The overall reaction in a silver cell used in watch batteries is Ag2O(s) + H2O(l) + Zn(s) → 2Ag(s) + Zn(OH)2(s) The half‑equation for the reaction at the positi
October 2021, Unit 5, Q1(a) (1 mark): Which material should be used for each electrode? (1) Electrode 1 Electrode 2 A Na2Cr2O7 Cr2O3 H2 Cr B Pt Cr C Pt Pt D
October 2021, Unit 5, Q1(b) (1 mark): Solution 1 is (1) A 0.33 mol dm–3 H3PO4(aq) B 0.50 mol dm–3 H2SO4(aq) C 1.00 mol dm–3 HCl(aq) D 1.00 mol dm–3 CH3COOH(aq)
October 2021, Unit 5, Q1(c) (1 mark): Solution 2 contains 14.71 g of K2Cr2O7 . What mass of Cr2(SO4)3⋅18H2O should also be used? Cr2(SO4)3⋅18H2O = 716.3] [Mr values: K2Cr2O7 = 294.2 (1) A 8.95 g B 1
October 2021, Unit 5, Q1(d) (1 mark): Solution 2 is best acidified with (1) A H2SO4 B HCl C HBr D H2CrO4 Use this space for any rough working. Anything you write in this space will gain no credit.
October 2021, Unit 5, Q2 (1 mark): The equation for a redox reaction is 5Fe2+(aq) + MnO 4 –(aq) + 8H+(aq) → 5Fe3+(aq) + Mn2+(aq) + 4H2O(l) Which is the correct cell diagram to measure E d cell fo
October 2021, Unit 5, Q3 (1 mark): Some standard electrode potentials are shown. Electrode system E d / V Bk3+ + e–  Bk2+ –2.80 Cu2+ + e–  Cu+ +0.15 +1.67 Bk4+ + e–  Bk3+ Au+ + e– +1.69  Au A
October 2021, Unit 5, Q20(c)(iv) (1 mark): Use the electrode potential data provided to calculate E d cell for the overall titration reaction. (1)
October 2021, Unit 6, Q1(c)(i) (1 mark): Calculate E d cell for the electrochemical cell. (1)
October 2021, Unit 6, Q1(c)(ii) (3 marks): A student drew a diagram of an experiment to measure the standard emf of the cell. low voltage supply copper iron solution containing solution containing Cu2+(a
June 2021, Unit 5, Q2(a) (1 mark): The electrode potential for the Fe3+/ Fe2+ electrode system is +0.77 V. What is the electrode potential for the Ti2+/Ti electrode system? (1) A −3.17 V B −1.63
June 2021, Unit 5, Q2(b) (1 mark): What metals should be used for the electrodes in the cell for this reaction? (1) Metals used for the electrode Fe3+/ Fe2+ electrode system Ti2+/ Ti electrode sy
June 2021, Unit 5, Q2(c) (1 mark): The half-cell for the Fe3+/ Fe2+ electrode system is prepared by mixing equal volumes of solutions of iron(II) sulfate, FeSO4, and iron(III) sulfate, Fe2(SO4)3.
June 2021, Unit 5, Q18(a)(i) (2 marks): Write the ionic equation for the disproportionation of manganate(VI) ions, MnO4 2−, in acidic conditions, using relevant half-equations from the table. State sy
June 2021, Unit 5, Q18(a)(ii) (2 marks): Calculate O conditions, stating whether or not the reaction is thermodynamically feasible. (2)
June 2021, Unit 5, Q18(a)(iii) (4 marks): Using the standard electrode potentials in the table, assess the thermodynamic feasibility of preparing manganate(VI) by reacting manganate(VII) and manganese(I
January 2021, Unit 5, Q1 (1 mark): When an alkene is added to a solution of potassium manganate(VII), the purple solution turns colourless. In terms of electron transfer and oxidation number, how
January 2021, Unit 5, Q2 (1 mark): The standard hydrogen electrode uses an electrode of platinum coated in a finely divided form of the metal called platinum black. What is the purpose of this co
January 2021, Unit 5, Q3(a) (1 mark): What is the cell diagram for this cell? (1) A Fe(s) | Fe2+(aq) || Sn(s) | Sn2+(aq) B Fe2+(aq) | Fe(s) || Sn2+(aq) | Sn(s) C Fe(s) | Fe2+(aq) || Sn2+(aq) | Sn(s)
January 2021, Unit 5, Q3(b) (1 mark): The standard electrode potential for the Fe / Fe2+ electrode system is −0.44 V and E d cell for the reaction is +0.30 V. What is the standard electrode potentia
January 2021, Unit 5, Q19(c)(ii) (2 marks): Show that the reaction in (c)(i) is thermodynamically feasible. Use the standard electrode potentials of the relevant half-cells from the Data Booklet. (2)
January 2021, Unit 5, Q21(a) (2 marks): Deduce the formulae of the ions responsible for the colours of F and G, using the standard electrode potential and E d given, and the values in the Data Booklet
January 2021, Unit 5, Q21(b) (2 marks): Write the overall equation for the reaction in the cell. State symbols are not required. (2)
October 2020, Unit 5, Q21(a) (3 marks): The half-equation for an iron(III) / iron(II) half-cell is Fe3+(aq) + e− ⇌ Fe2+(aq) The standard electrode potential of this half-cell is measured using the app
October 2020, Unit 5, Q21(b) (3 marks): The cell diagram for an electrochemical cell is — O Pt | [Mn2+ + 4H2O], [MnO4 − + 8H+] [BiO3 − + 6H+], [Bi3+ + 3H2O] | Pt E cell = +0.09 V Write the half-equati
October 2020, Unit 5, Q21(c) (2 marks): The standard electrode potential, E Cr3+(aq) + 3e− ⇌ Cr(s) The effect on the electrode potential, E, of changing the concentration of the ions in the half cell

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