Question

In chlor-alkali process, and are released at cathode and anode respectively.

• A. ${\mathrm{Cl}}_2$
• B. $H_2$
• C. $O_2$
• D. $\mathrm{NaCl}$

Answer 1

Answer: (A), (B)

$H_2$

The chlor-alkali process is an industrial process for the electrolysis of sodium chloride solution (brine).

Reactions involved:
At anode (oxidation): ${\text{2Cl}}^{-}\text{(aq)}\to {\text{Cl}}_2\text{(g)}+2{\text{e}}^{-}$
At cathode (reduction): ${\text{2H}}_2\text{O}\text{(l)}+2{\text{e}}^{-}\to {\text{H}}_2\text{(g)}+2{\text{OH}}^{-}$
Overall reaction: $\text{2NaCl}\text{(s)}+2{\text{H}}_2\text{O}\text{(l)}\to {\text{Cl}}_2\text{(g)}+{\text{H}}_2\text{(g)}+2\text{NaOH (aq)}$

Hence, chlorine gas is released at anode and hydrogen gas at cathode as shown in the diagram:


In the given figure, 'A' is chlorine gas, 'B' is NaOH and 'C' is hydroxide ions.