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Standard electrode potentials for a few half cells are mentioned below: E°Cu2+/Cu = 0.34V; E°Zn2+/Zn = −0.76 V E°Ag+/Ag = 0.80 V; E°Mg2+/Mg = −2.37 V Which one of the following cells gives the most negative value of ΔG° ?

1. (1) Zn | Zn2+(1M) | | Ag+(1M) | Ag
2. (2) Zn | Zn2+(1M) | | Mg2+(1M) | Mg
3. (3) Ag | Ag+(1M) | | Mg2+(1M) | Mg
4. (4) Cu | Cu2+(1M) | | Ag+(1M) | Ag

Correct answer: (1) Zn | Zn2+(1M) | | Ag+(1M) | Ag

Solution

The cell with Zn and Ag has the largest potential difference, as Zn is a strong reducing agent and Ag is a strong oxidizing agent. This results in a more negative Gibbs free energy change (ΔG°), indicating a more spontaneous reaction.

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