In the button cells widely used in watches and other devices, the following reaction takes place:
`Zn (s) + Ag_(2)O (s) + H_2O (l) to Zn^(2+) (aq) + 2Ag (s) + OH^(-)` (aq)
Determine `E^(@)` and `Delta_(r)G^(@)` for the reaction.

Explanation

Electrode reactions taking place in the button cell are as under :
`Zn(s) to Zn^(2+)(aq) + 2e^(-)`
`2Ag^(+)(aq) + 2e^(-) to 2Ag(s)`
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`Zn(s) + 2Ag^(+)(aq) to Zn^(2+)(aq) + 2Ag(s)`
Thus, n=2
`E^(@)` for the reaction can be obtained as under:
`E_("cell")^(@) = (E_("cathode")^(@) - E_("anode")^(@))`
`=+0.80 V - (0.76 V) = + 1.56 V`
Use the following relation to calculate `Delta_(r)G^(@)`
`Delta_(r)G^(@) =-nE^(@) F`
`=-301.080 kJ mol^(-1)`