In the electrolysis of brine using neutral electrode, which ion is discharged at the anode?

Answer Details

Brine is a concentrated solution of sodium chloride (NaCl) in water. When brine is electrolysed using inert (neutral) electrodes such as carbon or platinum, the ions present in solution are:

• Cations: Na⁺ and H⁺ (from water)
• Anions: Cl^- and OH^- (from water)

At the anode (positive electrode), anions migrate and are discharged. Both Cl^- and OH^- are present, but Cl^- is preferentially discharged because it is present in much higher concentration in the brine solution. Despite OH^- having a lower discharge potential, the high concentration of Cl^- gives it priority at the anode.

The half-equation at the anode is:

\[2\text{Cl}^- \rightarrow \text{Cl}_2 + 2e^-\]

Chlorine gas (Cl₂) is released at the anode.

Na⁺ and H⁺ are cations and migrate to the cathode, not the anode. At the cathode, H⁺ is discharged (since Na⁺ has a very high discharge potential), producing hydrogen gas.