Question

Choose the correct option regarding the substances which are liberated at the cathode and anode during the electrolysis of aqueous NaCl.

• A. Anode: $\text{Na (s)}$; Cathode: ${\text{H}}_2\text{O (l)}$
• B. Anode: $\text{Na (s)}$; Cathode: ${\text{Cl}}_2\text{(g)}$
• C. Anode: ${\text{Cl}}_2\text{(g)}$; Cathode: ${\text{H}}_2\text{(g)}$
• D. Anode: ${\text{H}}_2\text{(g)}$; Cathode: $\text{Na (s)}$

Answer 1

The correct option is C Anode: ${\text{Cl}}_2\text{(g)}$; Cathode: ${\text{H}}_2\text{(g)}$

When electricity is passed through an aqueous solution of sodium chloride (called brine), it results in formation of sodium hydroxide solution. This process is called chlor-alkali process.
The reaction involved is:
$2NaCl\left(aq\right)+2H_{2}O\left(l\right)\to 2NaOH\left(aq\right)+C{l}_2\left(g\right)+H_2\left(g\right)$
Chlorine gas is given out at the anode, and hydrogen gas at the cathode. Sodium hydroxide solution is formed near the cathode.