(a) The diagram shows the apparatus used to measure the standard electrode potential, E°, of Fe³⁺(aq)/Fe²⁺(aq). [Figure showing apparatus for standard electrode potential measurement, with labels A-F]

1. (a)(i)Identify what the letters A to F represent. A B C D E F[3]
2. (a)(ii)Label the diagram to show • which is the positive electrode, • the direction of electron flow in the external circuit. Use the Data Booklet to help you.[1]
3. (b)In another experiment, an Fe³⁺(aq)/Fe²⁺(aq) half-cell was connected to a Cu²⁺(aq)/Cu(s) half-cell. Determine the standard cell potential, E°cell, when these two half-cells are connected by a wire and the circuit is completed. Use the Data Booklet to help you. E°cell = V [1][1]
4. (c)(i)The E° of Ni²⁺(aq)/Ni(s) is −0.25V. State and explain how the electrode potential changes if the concentration of Ni²⁺(aq) is decreased.[1]
5. (c)(ii)The E° of Cr³⁺(aq)/Cr²⁺(aq) is -0.41 V. Calculate the electrode potential when [Cr³⁺(aq)] is 0.60 mol dm⁻³ and [Cr²⁺(aq)] is 0.15 mol dm⁻³. Use the Nernst equation. E = E° + 0.059/z log [oxidised species]/[reduced species] E = V [2][2]

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