Standard electrode potentials for a few half cells are menti... | Chemistry - Electrochemical Cells and Standard Electrode Potentials | SolveeIt

Question

Standard electrode potentials for a few half cells are mentioned below : $E_{Cu^{2+}/Cu}^o = 0.34 \ V, E_{Zn^{2+}/Zn}^o = -0.76 \ V$ $E_{Ag^{+}/Ag}^o = 0.80 \ V, E_{Mg^{2+}/Mg}^o = -2.37 \ V$ Which one of the following cells gives the most negative value of $\Delta G^o$ ?

$Zn|Zn^{2+}(1M)||Ag^{+}(1M)|Ag$

$Zn|Zn^{2+}(1M)||Mg^{2+}(1M)|Mg$

$Ag|Ag^{+}(1M)||Mg^{2+}(1M)|Mg$

$Cu|Cu^{2+}(1M)||Ag^{+}(1M)|Ag$

Answer

Zn|Zn²⁺(1 M)||Ag⁺(1 M)|Ag

Explanation

Solution

In a galvanic cell, ΔG° = –nFE°₍cell₎. Thus, a higher positive E°₍cell₎ gives a more negative ΔG°.
The cell notation convention shows the left electrode as oxidation and the right as reduction. So, E°₍cell₎ = E°₍red (right)₎ – E°₍red (left)₎.
Option A: Zn|Zn²⁺ (E°₍red₎ = –0.76 V) is oxidized and Ag⁺|Ag (E°₍red₎ = +0.80 V) is reduced.
- E°₍cell₎ = 0.80 V – (–0.76 V) = 1.56 V.
Higher E°₍cell₎ yields a more negative ΔG°. Options that yield a negative E°₍cell₎ are non‐spontaneous, and the other option (D) gives a lower E°₍cell₎.

Question: Standard electrode potentials for a few half cells are mentioned below : $E_{Cu^{2+}/Cu}^o = 0.34 \ ...

Solution