Question

The standard reduction potential for \[\ce{Zn{^{2+}_{(aq)}} | Zn_{(s)}}\] half cell is −0.76 V. Write the reactions occurring at the electrodes when coupled with NHE.

Answer 1

Given: The standard reduction potential for \[\ce{Zn{^{2+}_{(aq)}} | Zn_{(s)}}\] half cell is −0.76 V.

NHE = Normal Hydrogen Electrode with standard electrode potential = 0.00 V

Zn²⁺ has lower E° (–0.76 V) than SHE (0.00 V).

Therefore, Zn electrode acts as anode (oxidation occurs here).

SHE acts as cathode (reduction occurs here).

At anode: \[\ce{Zn_{(s)} -> Zn{^{2+}_{(aq)}} + 2e-}\]

At cathode: \[\ce{2H{^{+}_{(aq)}} + 2e- -> H2_{(g)}}\]

Overall cell reaction: \[\ce{Zn_{(s)} + 2H{^{+}_{(aq)}} -> Zn{^{2+}_{(aq)}} + H2_{(g)}}\]