Question

Which among the following is correct for electrolysis of brine solution ?

• A. $O_2$ gas is liberated at cathode
• B. Sodium metal is collected at anode
• C. $H_2$ gas is liberated at cathode
• D. $Cl_2$ gas is liberated at cathode

Answer 1

Answer: (C)

$H_2$ gas is liberated at cathode

Answer 2

In electrolysis of brine solution, $H _{2}$ gas is liberated at cathode. The solution contains four ions $Na ^{+}, Cl ^{?}, H ^{+}$ and $\overset{?}{O} H$ ions. There occurs a race amongst them for their discharge at their respective electrodes.

Following electrode reactions are possible:

Cathode $2 H _{2} O (l)+2 e^{-} \longrightarrow H _{2}(g)+2 \overset{-}{{O}} H (aq)$

Anode $2 Cr ( aq ) \longrightarrow Cl _{2}( g )+2 e^{-}$

In this electrolysis, $H _{2}$ at cathode and $Cl _{2}$ at anode are given off.