Question

Dihydrogen of high purity (>99.95%) is obtained through:

• A. The electrolysis of acidified water using $Pt$ electrodes.
• B. The electrolysis of warm $Ba(OH{)}_2$ solution using $Ni$ electrodes.
• C. The reaction of $Zn$ with dilute $HCl$
• D. The electrolysis of brine solution.

Answer 1

The correct option is B The electrolysis of warm $Ba(OH{)}_2$ solution using $Ni$ electrodes.

Pure hydrogen gas can be obtained by the electrolysis of warm $Ba(OH{)}_2$ solution using $Pt$ or $Ni$ electrodes. As water does not conduct electricity very well, it is usual to electrolyse aqueous solution of $Ba(OH{)}_2$. The gases produced at anode and cathode must be kept seperate.
Reactions occusirng at anode and cathode are:
Anode:
$2O{H}^{-}\to H_{2}O+\frac{1}{2}{O}_2+2e^{-}$
Cathode:
$2H_{2}O+2e^{-}\to 2O{H}^{-}+H_2$
Overall reaction being
$H_{2}O\to H_2+\frac{1}{2}{O}_2$
Option (b) is correct.