Battery engineers wish to design a galvanic cell that delivers a standard cell potential of at least +0.60 V while using only the metals and ions listed in the table below. All reactant and product species are at standard conditions.
Standard reduction potentials (25 °C):
1. Cl2(g) + 2 e⁻ → 2 Cl⁻(aq) E° = +1.36 V
2. Fe3+(aq) + e⁻ → Fe2+(aq) E° = +0.77 V
3. Cu2+(aq) + 2 e⁻ → Cu(s) E° = +0.34 V
4. Pb2+(aq) + 2 e⁻ → Pb(s) E° = −0.13 V
(a) Select one species from the table to undergo reduction and a different species to undergo oxidation so that the resulting galvanic cell has E°cell ≥ +0.60 V. State clearly which half-reaction is written as a reduction and which is written as an oxidation.
(b) Balance the two chosen half-reactions for both mass and charge and combine them to give the overall redox reaction occurring in the cell.
(c) Calculate the standard cell potential E°cell for the overall reaction from part (b).
(d) Determine the standard free-energy change ΔG° (in kJ mol⁻¹) for the reaction you have designed. Comment on whether the sign and magnitude of ΔG° meet the engineers’ requirement for a thermodynamically favorable process that can perform useful electrical work.