Electrolysis

Electrolysis

It is the process in which a non-spontaneous reaction is carried out by using electrical energy.

This reaction is used :
❖ production of hydrogen for fuel.
❖ in layering metals to fortify them.
❖ in production of oxygen for space craft and nuclear submarines.
❖ in electrolytic etching of metal surfaces like tools or knives with a permanent mark or logo.

electrometallurgy, which is the process of reduction of metallic compound into pure metal by electrolysis.

1. Strong electrolytes

The electrolytes which are almost completely dissociated into ions in solution are called strong electrolytes.
Example — NaCl, KCl, HCl, NaOH etc.

2. Weak electrolytes

The electrolytes which do not ionise completely in solution are called weak electrolytes.
Example—CH₃COOH, H₂CO₃, HCN, ZnCl₂, NH₄OH etc.

3. Electrolysis

The process of chemical decomposition of an electrolyte by passage of electric current through its molten state or its solution is called electrolysis.

4. Electrodes

In order to pass the current through an electrolytes in molten state or in aqueous solution, two rods or plates are needed to connect with the terminal of a battery. These rods or plates are called electrodes.

» Anode
The electrode which is attached to positive terminal of battery is called anode. Oxidation occurs at anode.

» Cathode
The electrode which is attached to negative terminal of batteries is called, Reduction occurs at cathode.

Examples — Electrolysis of molten NaCl
At anode: Cl^- - e → Cl
Cl + Cl → Cl₂
At cathode : Na⁺ + e → Na

So, Cl₂ gas occurs at anode while Na at cathode.