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Question
Following reactions occur at cathode during the electrolysis of aqueous silver chloride solution :
`Ag^+(aq)+e^(-)rarrAg(s)" "" "" "E^@=+0.80V`
`H^+(aq)+e^(-)rarr1/2H_2(g)" "" "" " E^@=0.00V`
On the basis of their standard reduction electrode potential (E°) values, which reaction is feasible at the cathode and why ?
Solution
Given :
`Ag^+(aq)+e^(-)rarrAg(s)" "" "" "E^@=+0.80V`
`H^+(aq)+e^(-)rarr1/2H_2(g)" "" "" " E^@=0.00V`
The relationship between the standard free energy change and emf of a cell reaction is given by
ΔG° = −nFE°
Thus, the more positive the standard reduction potential of a reaction, the more negative is the standard free energy change associated with the process and, consequently, the higher is the feasibility of the reaction.
Since E∘Ag+/AgE∘Ag+/Ag has a greater positive value than E∘H+/HE∘H+/H, the reaction which is feasible at the cathode is given by
Ag+(aq) + e− → Ag(s)
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