Question

The standard electrode potentials for two half-equations for the silver–zinc cell are Ag₂O(s) + H₂O(l) + 2e– → 2Ag(s) + 2OH⁻(aq), E° = 0.34 V and ZnO(s) + H₂O(l) + 2e– → Zn(s) + 2OH⁻(aq), E° = –1.26 V. Give an equation for the overall reaction that occurs when the cell is recharging.

Answer 1

The overall reaction that occurs when the silver-zinc cell is recharging is 2Ag(s) + 2OH⁻(aq) → Ag₂O(s) + H₂O(l) + 2e–.

Step-by-step explanation:

The overall reaction that occurs when the cell is recharging can be determined by reversing the reduction half-reaction at the cathode and the oxidation half-reaction at the anode.

The reduction half-reaction at the cathode is Ag₂O(s) + H₂O(l) + 2e– → 2Ag(s) + 2OH⁻(aq) with a standard electrode potential (E°) of 0.34 V.

The oxidation half-reaction at the anode is ZnO(s) + H₂O(l) + 2e– → Zn(s) + 2OH⁻(aq) with a standard electrode potential (E°) of -1.26 V.

When these two equations are reversed and added together, the overall reaction that occurs during recharging is:

2Ag(s) + 2OH⁻(aq) → Ag₂O(s) + H₂O(l) + 2e–

The overall cell reaction is the sum of the oxidation and reduction half-reactions at the anode and cathode, respectively.