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For the cell Zn(s) | Zn^{2+}(aq) || M^{x+}(aq) | M(s), different half cells and their standard electrode potentials are given below: M^{x+}(aq) / M(s): Au^{3+}(aq) / Au(s), Ag^{+}(aq) / Ag(s), Fe^{3+}(aq) / Fe^{2+}(aq), Fe^{2+}(aq) / Fe(s) E^0 (V): 1.40, 0.80, 0.77, -0.44 If E^0_{Zn^{2+}/Zn} = -0.76 V, which cathode will give maximum value of E^0_{cell} per electron transferred?

1. Ag^{+}(aq) / Ag(s)
2. Fe^{3+}(aq) / Fe^{2+}(aq)
3. Au^{3+}(aq) / Au(s)
4. Fe^{2+}(aq) / Fe(s)

Correct answer: Fe^{3+}(aq) / Fe^{2+}(aq)

Solution

The cathode that provides the maximum cell potential is the one with the highest standard electrode potential. In this case, Fe^{3+}/Fe^{2+} has a potential of 0.77 V, which, when combined with the anode potential of Zn, results in the highest overall cell potential.

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