Galvanic Cell Summary

Key Concepts and Summary

Galvanic cells are devices in which a spontaneous redox reaction occurs indirectly, with the oxidant and reductant redox couples contained in separate half-cells. Electrons are transferred from the reductant (in the anode half-cell) to the oxidant (in the cathode half-cell) through an external circuit, and inert solution phase ions are transferred between half-cells, through a salt bridge, to maintain charge neutrality. The construction and composition of a galvanic cell may be succinctly represented using chemical formulas and others symbols in the form of a cell schematic (cell notation).

Practice Questions

Balance each reaction below, and write a cell schematic representing the reaction as it would occur in a galvanic cell.

(a) $Ag^+(aq)+NO(g)⟶Ag(s)+NO_3^-(aq)\quad \text{(acidic solution)}$


(b) $SiO_3^{2-}(aq)+Mg(s)⟶Si(s)+Mg(OH)_2(aq)\quad \text{(basic solution)}$


(c) $ClO_3^-(aq)+MnO_2(s)⟶Cl^-(aq)+MnO_4^-(aq)\quad \text{(basic solution)}$



a) Overall: $3Ag^+(aq)+NO(g)+2H_2O(l)⟶3Ag(s)+NO_3^-(aq)+4H^+(aq)$

$NO(g)$ | $NO_3^-(aq)$ || $Ag^+(aq)$ | $Ag(s)$

b) Overall: $2Mg(s)+SiO_3^{2-}(aq)+3H_2O(l)⟶2Mg(OH)_2(s)+si(s)+2OH^-(aq)$

$Mg(s)$ | $Mg(OH)_2(s)$ || $SiO_3^{2-}(aq)$ | $Si(s)$

c) Overall: $2MnO_2(s)+ClO_3^-(aq)+2OH^-(aq)⟶2MnO_4^-(aq)+H_2O(l)+Cl^-(aq)$

$Pt$ | $MnO_2(s)$ | $MnO_4^-(aq)$ || $ClO_3^-(aq)$, $Cl^-(aq)$ | $Pt$

Identify the oxidant and reductant in each reaction of the previous exercise.


Species oxidized = reducing agent: (a) NO(g); (b) Mg(s); and (c) MnO2(s); Species reduced = oxidizing agent: (a) Ag+(aq); (b) $SiO_3^-(aq)$; and (c) $ClO_3^-(aq)$