Question

In the electrolysis of aqueous $NaCl$ solution, side reactions taking place are :
(I) $2O{H}^{-}+C{l}_2\stackrel{}{\to }2OC{l}^{-}+H_2$
(II) $2Na+2H_{2}O\stackrel{}{\to }2NaOH+H_2$
(III) $4O{H}^{-}\stackrel{}{\to }{O}_2+2H_2+4e^{-}$
Select the correct alternate.

• A. I, II
• B. II, III
• C. I, III
• D. I, II and III

Answer 1

Answer: (A)

I, II

Chlorine is prepared by the electrolysis of brine solution in Nelson, Castner-Kelner or Salvey cell.
Chlorine is obtained at anode.
The side reactions that occur at anode are
(i) $2O{H}^{-}+C{l}_2\stackrel{}{\to }2OC{l}^{-}+H_2$
Hydroxide ion reacts with chlorine to produce hydrogen gas.
(ii) $2Na+2H_{2}O\stackrel{}{\to }2NaOH+H_2$
Sodium reacts with water to produce hydrogen gas.