Question # In the button cells widely used in watches and other devices the following reaction takes place:

# 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.

Solution

[

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}

]