In a fuel cell methanol is used as fuel and oxygen gas is used as an oxidizer. The reaction is
$\mathrm{C}{\mathrm{H}}_3\mathrm{O}\mathrm{H}\left(\mathrm{l}\right)+\frac{3}{2}{\mathrm{O}}_2\left(\mathrm{g}\right)\to \mathrm{C}{\mathrm{O}}_2\left(\mathrm{g}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$
At 298 K standard Gibb’s energies of formation for $\mathrm{C}{\mathrm{H}}_3\mathrm{O}\mathrm{H}\left(\mathrm{l}\right),\mathrm{ }{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$ and $\mathrm{C}{\mathrm{O}}_2\left(\mathrm{g}\right)$ are -166.2, -237.2 and -394.4 $\mathrm{k}\mathrm{J}\mathrm{ }{\mathrm{m}\mathrm{o}\mathrm{l}}^{-1}$ respectively. If standard enthalphy of combustion of methanol is -726 ${\mathrm{kJmol}}^{-1}$ , efficiency of the fuel cell will be