Commercial applications of electrochemical cells: AQA A‑Level Chemistry questions

AQA A-Level Chemistry past-paper questions on 3.1.11.2 Commercial applications of electrochemical cells, 2008–2025, with mark schemes and examiner’s reports where available.

All 80 questions on Commercial applications of electrochemical cells, as a list

June 2025, Paper 1, Q06.1 (2 marks): Give a half-equation for the reaction occurring, in alkaline conditions, at each electrode. [2 marks] At negative electrode At positive electrode
June 2025, Paper 1, Q06.2 (1 mark): Suggest why it is not necessary to replace the KOH electrolyte during the operation of this fuel cell. [1 mark]
June 2025, Paper 1, Q06.3 (2 marks): Describe how the reactions at the electrodes generate an electric current that can power the motor in the external circuit. [2 marks]
June 2025, Paper 1, Q06.4 (1 mark): This fuel cell uses pure oxygen, rather than air, as an oxidising agent. Suggest the identity of the gas in air that would react with the KOH and affect the eff
June 2025, Paper 1, Q06.5 (1 mark): When an alkaline hydrogen-oxygen fuel cell is used to power the motor in a car, the hydrogen can be stored as a liquid. Suggest an advantage of storing hydrogen
June 2025, Paper 1, Q06.6 (1 mark): Which graph shows the change in EMF, with time, for an alkaline hydrogen-oxygen fuel cell? [1 mark] Tick () one box. A B C
June 2025, Paper 1, Q06.7 (1 mark): An acidic hydrogen-oxygen fuel cell has different reactions at the electrodes. Suggest why the EMF of the acidic hydrogen-oxygen fuel cell is the same as that o
June 2024, Paper 1, Q09.7 (1 mark): In a lithium cell, a lithium cobalt oxide electrode and a lithium electrode are used. Give the equation for the reaction that occurs at the positive electrode.
June 2024, Paper 1, Q09.8 (1 mark): Commercial electrochemical cells can be rechargeable or non-rechargeable. State why lithium cells can be recharged. [1 mark]
June 2024, Paper 3, Q17 (1 mark): A cell with EMF = +2.15 V is made from two electrodes. The half-equations for the two electrodes are shown. positive electrode: PbO2(s) + 3 H+(aq) + HSO4–(aq) +
June 2023, Paper 1, Q08.1 (1 mark): At the positive electrode, oxygen reacts with hydrogen ions to form water. Give a half-equation for this reaction. [1 mark]
June 2023, Paper 1, Q08.2 (1 mark): At the negative electrode, methanol reacts with water to produce carbon dioxide and hydrogen ions. Give a half-equation for this reaction. [1 mark]
June 2023, Paper 1, Q08.3 (1 mark): The standard electrode potential for the CO2 / CH3OH electrode is +0.03 V Calculate the standard electrode potential for the O2 / H2O electrode. [1 mark]
June 2023, Paper 1, Q08.4 (1 mark): State why a fuel cell does not need to be electrically recharged. [1 mark]
June 2023, Paper 1, Q08.5 (1 mark): Suggest one advantage of using methanol, rather than hydrogen, in a fuel cell for use in cars. [1 mark]
June 2022, Paper 1, Q08.1 (1 mark): The half-equations for two electrodes that combine to make a non-rechargeable cell are Zn2+(aq) + 2e− → Zn(s) E o = −0.76 V 2 MnO2(s) + 2 NH4+(aq) + 2e– → Mn2O3
June 2022, Paper 1, Q08.2 (1 mark): Suggest the function of the porous separator in Figure 1. [1 mark]
June 2022, Paper 1, Q08.3 (1 mark): The standard electrode potentials for two half-equations for the silver–zinc cell are Ag2O(s) + H2O(l) + 2e–  2 Ag(s) + 2 OH–(aq) E o = +0.34 V ZnO(s) + H2O(l)
June 2022, Paper 1, Q08.4 (2 marks): Give the half-equation for the other electrode and calculate its standard electrode potential. [2 marks] Equation E o
June 2022, Paper 1, Q08.5 (1 mark): Suggest why the EMF values of the acidic and alkaline hydrogen–oxygen fuel cells are the same. [1 mark]
November 2021, Paper 1, Q09.1 (2 marks): Use data in Table 9 to explain why an aqueous electrolyte is not used for a lithium cell. [2 marks]
November 2021, Paper 1, Q09.2 (1 mark): In the 1970s lithium-iodine cells became a common power source for heart pacemakers. Lithium iodide is the final product of the cell reaction. Use the data in T
November 2021, Paper 1, Q09.5 (1 mark): Give an equation for the reaction that occurs at the positive lithium cobalt oxide electrode. [1 mark]
November 2021, Paper 1, Q09.6 (1 mark): Give an equation for the reaction that occurs at the negative lithium electrode. [1 mark]
November 2020, Paper 1, Q11.1 (1 mark): Deduce the half-equation for the reaction at the negative electrode. [1 mark]
November 2020, Paper 1, Q11.2 (1 mark): Deduce the half-equation for the reaction at the positive electrode. [1 mark]
November 2020, Paper 1, Q11.3 (1 mark): Give the equation for the overall reaction that occurs in the Glucose–oxygen fuel cell. [1 mark]
November 2020, Paper 1, Q11.4 (2 marks): The negative electrode is made of carbon and the positive electrode is made of platinum. Give the conventional representation for the glucose–oxygen fuel cell.
November 2020, Paper 1, Q11.5 (1 mark): State what must be done to maintain the EMF of this fuel cell when in use. [1 mark]
Specimen, Paper 1, Q03.4 (1 mark): EMF = V
Specimen, Paper 1, Q03.5 (1 mark): 8
June 2016, CHEM5 (old spec), Q5(a)(i) (3 marks): Write a half-equation for the reaction that occurs at each electrode. Use the half-equations to deduce an overall equation for the cell. [3 marks] Half-equation
June 2016, CHEM5 (old spec), Q5(a)(ii) (2 marks): State and explain the effect, if any, of increasing the pressure of oxygen on the e.m.f of this cell. [2 marks] Effect on e.m.f. Explanation
June 2016, CHEM5 (old spec), Q5(b) (1 mark): Complete the diagram to show how the e.m.f. of a hydrogen–oxygen fuel cell changes with time. [1 mark] time e.m.f.
June 2016, CHEM5 (old spec), Q5(c)(i) (1 mark): Suggest the effect, if any, on the e.m.f. of this cell if the surface area of each platinum electrode is increased. [1 mark]
June 2016, CHEM5 (old spec), Q5(c)(ii) (1 mark): State the main environmental advantage of using a hydrogen–oxygen fuel cell to power a car. [1 mark]
June 2016, CHEM5 (old spec), Q5(d) (1 mark): Suggest why the use of a hydrogen–oxygen fuel cell might not be carbon-neutral. [1 mark]
June 2014, CHEM5 (old spec), Q5(f)(i) (1 mark): Use data from Table 3 to calculate the e.m.f. of this cell. [1 mark] Answer =
June 2014, CHEM5 (old spec), Q5(f)(ii) (1 mark): Use half-equations from Table 3 to construct an overall equation for the cell reaction. [1 mark]
June 2014, CHEM5 (old spec), Q5(f)(iii) (2 marks): Identify which of A or B, in Figure 1, is the positive electrode. Give a reason for your answer. [2 marks] Positive electrode Reason
June 2014, CHEM5 (old spec), Q5(f)(iv) (1 mark): Suggest one reason, other than cost, why this type of cell is not recharged. [1 mark]
June 2014, CHEM5 (old spec), Q6(a)(i) (2 marks): Deduce half-equations for the electrode reactions in a hydrogen–oxygen fuel cell. [2 marks] Half-equation 1 Half-equation 2
June 2014, CHEM5 (old spec), Q6(a)(ii) (2 marks): Use these half-equations to explain how an electric current can be generated. [2 marks]
June 2014, CHEM5 (old spec), Q6(b) (1 mark): Explain why a fuel cell does not need to be recharged. [1 mark]
June 2014, CHEM5 (old spec), Q6(c) (1 mark): To provide energy for a vehicle, hydrogen can be used either in a fuel cell or in an internal combustion engine. Suggest the main advantage of using hydrogen in
June 2014, CHEM5 (old spec), Q6(d) (1 mark): Identify one major hazard associated with the use of a hydrogen–oxygen fuel cell in a vehicle. [1 mark] Section B Answer all questions in the spaces provided.
June 2013, CHEM5 (old spec), Q5(e)(i) (1 mark): The e.m.f. of this cell is 2.90 V. Use this information to calculate a value for the electrode potential of electrode B. (1 mark)
June 2013, CHEM5 (old spec), Q5(e)(ii) (2 marks): Write an equation for the overall reaction that occurs when this lithium cell is being recharged. (2 marks)
June 2013, CHEM5 (old spec), Q5(e)(iii) (1 mark): Suggest why the recharging of a lithium cell may lead to release of carbon dioxide into the atmosphere. (1 mark)
June 2012, CHEM5 (old spec), Q5(c)(i) (1 mark): Calculate the e.m.f. of this cell. (1 mark)
June 2012, CHEM5 (old spec), Q5(c)(ii) (1 mark): Write an equation for the overall reaction that occurs when the cell discharges. (1 mark)
June 2012, CHEM5 (old spec), Q5(c)(iii) (1 mark): Deduce one essential property of the non-reactive porous separator labelled in the diagram. (1 mark)
June 2012, CHEM5 (old spec), Q5(c)(iv) (1 mark): Suggest the function of the carbon rod in the cell. (1 mark)
June 2012, CHEM5 (old spec), Q5(c)(v) (1 mark): The zinc electrode acts as a container for the cell and is protected from external damage. Suggest why a cell often leaks after being used for a long time. (1 m
June 2012, CHEM5 (old spec), Q5(d)(i) (3 marks): Deduce the oxidation state of the nickel in this cell after recharging is complete. Write an equation for the overall reaction that occurs when the cell is rech
June 2012, CHEM5 (old spec), Q5(d)(ii) (1 mark): State one environmental advantage of this rechargeable cell compared with the non-rechargeable cell described in part (c). (1 mark)
June 2012, CHEM5 (old spec), Q5(e)(i) (1 mark): Deduce the equation for the overall reaction that occurs in the ethanol–oxygen fuel cell. (1 mark)
June 2012, CHEM5 (old spec), Q5(e)(ii) (1 mark): Deduce a half-equation for the reaction at the ethanol electrode. In this half-equation, ethanol reacts with water to form carbon dioxide and hydrogen ions. (1
June 2012, CHEM5 (old spec), Q5(e)(iii) (1 mark): The e.m.f. of an ethanol–oxygen fuel cell is 1.00 V. Use data from the table on page 10 to calculate a value for the electrode potential of the ethanol electrod
June 2011, CHEM5 (old spec), Q5(d)(iii) (1 mark): Suggest one reason why the cell cannot be electrically recharged. (1 mark)
June 2011, CHEM5 (old spec), Q5(e)(i) (1 mark): The PbO2/PbSO4 electrode is the positive terminal of the cell and the e.m.f. of the cell is 2.15 V. Use this information to calculate the missing electrode pote
June 2011, CHEM5 (old spec), Q5(e)(ii) (2 marks): A lead–acid cell can be recharged. Write an equation for the overall reaction that occurs when the cell is being recharged.
June 2011, CHEM5 (old spec), Q5(f)(i) (1 mark): Give one reason why the e.m.f. of the lead–acid cell changes after several hours. (1 mark)
June 2011, CHEM5 (old spec), Q5(f)(ii) (1 mark): Identify the type of cell that behaves like cell X. (1 mark)
June 2011, CHEM5 (old spec), Q5(f)(iii) (2 marks): Explain why the voltage remains constant in cell X. (2 marks)
January 2011, CHEM5 (old spec), Q5(a)(i) (3 marks): Identify the element that undergoes a change in oxidation state at the positive electrode and deduce these oxidation states of the element. Element Oxidation st
January 2011, CHEM5 (old spec), Q5(a)(ii) (1 mark): Write a half-equation for the reaction at the negative electrode during operation of the lithium ion cell. (1 mark)
January 2011, CHEM5 (old spec), Q5(a)(iii) (2 marks): Suggest two properties of platinum that make it suitable for use as an external electrical contact in the cell. Property 1 Property 2 (2 marks)
January 2011, CHEM5 (old spec), Q5(a)(iv) (1 mark): Suggest one reason why water is not used as a solvent in this cell. (1 mark)
June 2010, CHEM5 (old spec), Q7(b) (2 marks): A conventional representation of a lithium cell is given below. This cell has an e.m.f. of +2.91 V Li(s) | Li+(aq) || Li+(aq) | MnO2(s) , LiMnO2(s) | Pt(s) Writ
January 2010, CHEM5 (old spec), Q2(a) (1 mark): Calculate the e.m.f. of a nickel–cadmium cell. (1 mark)
January 2010, CHEM5 (old spec), Q2(b) (2 marks): Deduce an overall equation for the reaction that occurs in the cell when it is used. (2 marks)
January 2010, CHEM5 (old spec), Q3(b) (1 mark): Use data from the table to calculate the e.m.f. of a hydrogen–oxygen fuel cell operating in alkaline conditions. (1 mark)
January 2010, CHEM5 (old spec), Q3(c) (2 marks): Write the conventional representation for an alkaline hydrogen–oxygen fuel cell. (2 marks)
January 2010, CHEM5 (old spec), Q3(d) (2 marks): Use the appropriate half-equations to construct an overall equation for the reaction that occurs when an alkaline hydrogen–oxygen fuel cell operates. Show your
January 2010, CHEM5 (old spec), Q3(e) (1 mark): Give one reason, other than cost, why the platinum electrodes are made by coating a porous ceramic material with platinum rather than by using platinum rods. (1
January 2010, CHEM5 (old spec), Q3(f) (1 mark): Suggest why the e.m.f. of a hydrogen–oxygen fuel cell, operating in acidic conditions, is exactly the same as that of an alkaline fuel cell. (1 mark)
January 2010, CHEM5 (old spec), Q3(g) (1 mark): Other than its lack of pollution, state briefly the main advantage of a fuel cell over a re-chargeable cell such as the nickel– cadmium cell when used to provid
January 2010, CHEM5 (old spec), Q3(h) (1 mark): Hydrogen– oxygen fuel cells are sometimes regarded as a source of energy that is carbon neutral. Give one reason why this may not be true. (1 mark)
June 2008, CHM5 (2008 spec), Q4(b) (6 marks): 4 (b) An alkaline cell that is used to provide electricity has electrodes which can be represented by the following half-equations. The zinc electrode is the ne

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