Electrochemistry

For the cell involving following reaction.

\(\mathrm{Zn}_{(\mathrm{s})}+\mathrm{Ni}_{(\mathrm{aq})}^{+2} \longrightarrow \mathrm{Zn}_{(\mathrm{aq})}^{+2}+\mathrm{Ni}_{(\mathrm{s})}, \mathrm{E}_{\mathrm{cell}}^*=0.5 \mathrm{~V} .\)

What is standard Gibb's energy change of cell reaction?