8.30 :   Depict the galvanic cell in which the reaction Zn(s) + 2${\mathrm{Ag}}^{+}$(aq) → ${\mathrm{Zn}}^{2+}$+(aq) + 2Ag(s) takes place, further show:
(i) which of the electrode is negatively charged,
(ii)the carriers of the current in the cell, and (iii) the individual reaction at each electrode.

The galvanic cell corresponding to the given redox reaction can be represented as:
$\overline{)\mathrm{Zn}}Z{{n}^{2+}}_{\left(aq\right)}\parallel \overline{)A{{g}^{+}}_{\left(aq\right)}}Ag$

(i) Zn electrode is negatively charged because at this electrode, Zn oxidizes to ${\mathrm{Zn}}^{2+}$  and the leaving electrons accumulate on this electrode.
(ii) Ions are the carriers of current in the cell.
(iii) The reaction taking place at Zn electrode can be represented as:

${\mathrm{Zn}}_{\left(\mathrm{s}\right)}\to {{\mathrm{Zn}}^{2+}}_{\left(\mathrm{aq}\right)}+2{\mathrm{e}}^{-}$

And the reaction taking place at Ag electrode can be represented as:

${{\mathrm{Ag}}^{+}}_{\left(\mathrm{aq}\right)}+{\mathrm{e}}^{-}\to {\mathrm{Ag}}_{\left(\mathrm{g}\right)}$

(iv) In aqueous solutions,${\mathrm{CuCl}}_{2}$  ionizes to give ions as:

${\mathrm{CuCl}}_{2\left(\mathrm{aq}\right)}\to {{\mathrm{Cu}}^{2+}}_{\left(\mathrm{aq}\right)}+2{{\mathrm{Cl}}^{-}}_{\left(\mathrm{aq}\right)}$

On electrolysis, either of ${\mathrm{Cu}}^{2+}$ ions or ${\mathrm{H}}_{2}\mathrm{O}$ molecules can get reduced at the cathode. But the reduction potential of ${\mathrm{Cu}}^{2+}$ is more than that of ${\mathrm{H}}_{2}\mathrm{O}$molecules.

Hence, Cu2+ ions are reduced at the cathode and get deposited.
Similarly, at the anode, either of ${\mathrm{Cl}}^{-}$ or ${\mathrm{H}}_{2}\mathrm{O}$ is oxidized. The oxidation potential of ${\mathrm{H}}_{2}\mathrm{O}$ is higher than that of ${\mathrm{Cl}}^{-}$.

But oxidation of ${\mathrm{H}}_{2}\mathrm{O}$ molecules occurs at a lower electrode potential than that of ${\mathrm{Cl}}^{-}$ ions because of over-voltage (extra voltage required to liberate gas). As a result, ${\mathrm{Cl}}^{-}$ ions are oxidized at the anode to liberate ${\mathrm{Cl}}_{2}$ gas.