In the button cells widely used in watches and other devices the following reaction takes place:
[
begin{array}{l}
mathrm{Zn}(s)+mathrm{Ag}_{2} mathrm{O}(s)+mathrm{H}_{2} mathrm{O}(l) quad longrightarrow
quad mathrm{Zn}^{2+}(a q)+2 mathrm{Ag}(s)+2 mathrm{OH}^{-}(a q)
end{array}
]
Determine ( Delta_{r} G^{circ} ) and ( E^{circ} ) for the reaction.

[
begin{aligned}
E_{text {cell }}^{circ} &=E_{A g_{2}}^{circ} mathrm{O} / mathrm{Ag}-E_{mathrm{Zn}^{2+} / mathrm{Zn}}^{circ}
&=+0.344-(-0.76)=1.104 mathrm{V}
end{aligned}
]
For the given cell reaction, ( n=2 )
[
begin{aligned}
Delta_{r} G^{circ} &=-n F E_{mathrm{cell}}^{circ}
Delta_{r} G^{circ} &=-2 times 96500 times 1.104
&=-2.13 times 10^{5} mathrm{CV} mathrm{mol}^{-1}
&=-2.13 times 10^{5} mathrm{Jmol}^{-1}
end{aligned}
]