Question

Predict the products of electrolysis obtained at the electrodes in the case when the electrodes used are of platinum:

An aqueous solution of AgNO₃.

Predict the products of electrolysis in the case of the electrolysis of an aqueous solution of AgNO₃ using platinum electrodes.

Answer 1

When platinum electrodes are used for electrolysis of an aqueous solution of AgNO₃, the products at the electrodes are determined based on the ion discharge potentials.

\[\ce{AgNO3 -> Ag+ + NO3-}\]

Also, water partially ionises:

\[\ce{H2O <=> H+ + OH-}\]

At cathode (Reduction site):

Competing species: Ag⁺ and H⁺

\[\ce{Ag+ + e- -> Ag_{(s)}}\]; E° = +0.80 V

\[\ce{2H2O + 2e- -> H2_{(g)} + 2OH-}\]; E° = −0.83 V

Since Ag⁺ has a higher reduction potential, silver is deposited:

\[\ce{Ag+ + e- -> Ag_{(s)}}\]

At Anode (Oxidation Site):

Competing species: \[\ce{NO^-_3}\] and OH⁻

\[\ce{NO^-_3}\] is not oxidised under normal conditions.

\[\ce{4OH- -> O2_{(g)} +2 H2O + 4e-}\]

Hence, water is oxidised, evolving oxygen gas:

\[\ce{2H2O -> O2_{(g)} + 4H+ + 4e-}\]

Overall reaction is:

\[\ce{2AgNO3 + 2H2O -> 2Ag_{(s)} + O2_{(g)} + 2HNO3}\]