Data should be selected from Table 3.1 in order to answer some parts of this question. Table 3.1 electrode reaction | E°/V Mg²⁺ + 2e⁻ ⇌ Mg | -2.38 Mn²⁺ + 2e⁻ ⇌ Mn | -1.18 Mn³⁺ + e⁻ ⇌ Mn²⁺ | +1.49 MnO₂ + 4H⁺ + 2e⁻ ⇌ Mn²⁺ + 2H₂O | +1.23 MnO₄⁻ + e⁻ ⇌ MnO₄²⁻ | +0.56 MnO₄⁻ + 4H⁺ + 3e⁻ ⇌ MnO₂ + 2H₂O | +1.67 MnO₄⁻ + 8H⁺ + 5e⁻ ⇌ Mn²⁺ + 4H₂O | +1.52

1. (a)An electrochemical cell can be constructed from a Mg²⁺/Mg half-cell and a MnO₄⁻/Mn²⁺ half-cell. The standard cell potential of this cell can be calculated using the standard electrode potentials of the two half-cells.
2. (a)(i)Define standard electrode potential. Include details of the standard conditions used. [2][2]
3. (a)(ii)Complete the diagram below to show an electrochemical cell constructed from a Mg²⁺/Mg half-cell and a MnO₄⁻/Mn²⁺ half-cell. Label your diagram. [Figure 3.1: Two beakers with electrodes and salt bridge] [3][3]
4. (a)(iii)Use a positive (+) sign and a negative (-) sign to identify the polarity of each of the two electrodes in your diagram. Use an arrow and the symbol 'e' to show the direction of electron flow in the external circuit. [1][1]
5. (a)(iv)Calculate the standard cell potential, E°cell, of this cell. E°cell = .............................................. V [1][1]
6. (a)(v)Construct an equation for the cell reaction. [1][1]
7. (a)(vi)Predict how the cell reaction will change, if at all, when the solution in the Mg²⁺ / Mg half-cell is diluted by the addition of a large volume of water. Explain your answer. [1][1]
8. (b)A molten magnesium salt is electrolysed for 15.0 minutes by a constant current. 4.75 × 10²² magnesium atoms are produced at the cathode. Calculate the value of the current used. current = .............................................. A [2][2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.