Given: $E^{\circ }\left({\mathrm{Ag}}^{+}\mid \mathrm{Ag}\right)=0.799\mathrm{V}$ and $E^{\circ }\left({\mathrm{Zn}}^{2+}\mid \mathrm{Zn}\right)=-0.673\mathrm{V}$, which of the following is true?

Given: $E^{\circ }\left({\mathrm{Ag}}^{+}\mid \mathrm{Ag}\right)=0.799\mathrm{V}$ and $E^{\circ }\left({\mathrm{Zn}}^{2+}\mid \mathrm{Zn}\right)=-0.673\mathrm{V}$, 

From the above equation it is observed that  more positive potential will constitute positive terminal (i.e. cathode) and the ions will be reduced here. So ${\mathrm{Ag}}^{+}$ is reduced by ${\mathrm{H}}_2$ gas.

Hence, ${\mathrm{Ag}}^{+}$can be reduced by ${\mathrm{H}}_2$