Question

What are the criteria for product formation during electrolysis?

Answer 1

1. Nature of the electrolyte: If the electrolyte is aqueous, both the ions of the electrolyte and water can be oxidised or reduced. If the electrolyte is molten, only the ions of the electrolyte are involved.
2. Standard electrode potentials: At the cathode, the species with higher reduction potential is preferentially reduced. At the anode, the species with lower oxidation potential is preferentially oxidised.
3. Overvoltage (Overpotential): Some reactions (like oxygen evolution) require extra potential to occur. Due to high overvoltage, a less favourable ion may get discharged.
4. Concentration of ions: When multiple ions can be discharged, the ion present in higher concentration may be discharged first.
5. Nature of electrode: Inert electrodes (e.g., Pt, graphite) do not take part in the reaction. Active electrodes (e.g., Cu, Ag) may participate and influence the products.