During the chlor-alkali process for the industrial preparation of sodium hydroxide, electricity is passed through an aqueous solution of sodium chloride (brine). Which gases are liberated at the anode and cathode respectively?

Step-by-step solution

1. Step 1: Identify the chemical process. Brine is an aqueous solution of sodium chloride ($\text{NaCl}+{\text{H}}_2\text{O}$).
2. Step 2: Determine the reaction at the anode (positively charged electrode). Chloride ions (${\text{Cl}}^{-}$) are oxidized to form chlorine gas (${\text{Cl}}_2$).
3. Step 3: Determine the reaction at the cathode (negatively charged electrode). Hydrogen ions (${\text{H}}^{+}$) from water reduction form hydrogen gas (${\text{H}}_2$).
4. Step 4: Combine the observations to conclude that chlorine gas is released at the anode and hydrogen gas is released at the cathode.

Concept tested: Products of chlor-alkali process

Published 24 August 2026 · How this solution was prepared and checked

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