Standard electrode potentials for a few half cells are mentioned below : E Cu2+/Cu = 0.34 V, 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 G ?
- Zn | Zn2+(1M) || Ag+(1M) | Ag
- Ag | Ag+(1M) || Mg2+(1M) | Mg
- Zn | Zn2+(1M) || Mg2+(1M) | Mg
- Cu | Cu2+(1M) || Ag+(1M) | Ag
Answer
(1) Zn | Zn2+(1M) || Ag+(1M) | Ag
Solution
G =-nFE cell, E cell=E cathode-E anode; n=2 in all cells
(1) 0.80-(-0.76)=1.56 V; (2) -3.17 V; (3) -1.61 V; (4) 0.46 V
∴ largest positive E gives most negative G : cell (1)
Answer: (1)