Question

Write the principle of manufacture of sodium hydroxide by castner's process giving necessary equations

Answer 1

Manufacture of sodium hydroxide by castner's process:

The castner's process follows electrolysis of aqueous solution of NaCl to manufacture sodium hydroxide.

Explanation:

• Mercury is used as cathode and titanium is used as anode.
• When electric current is flowed through the electrode, positive and negative ions are produced.
• The ionisation of sodium chloride is given as:

$2 \mathrm{NaCl} \rightarrow 2 \mathrm{Na}^{+}+2 \mathrm{Cl}^{-}$

The reaction at cathode:

$2 \mathrm{Na}^{+}+2 \mathrm{e}^{-} \rightarrow 2 \mathrm{Na}$

The reaction at anode:

$2 \mathrm{Cl}^{-} \rightarrow \mathrm{Cl}_{2}+2 \mathrm{e}^{-}$

The mercury has sodium, when it is treated with water, it produces NaOH. It is formed as solid.

$2 \mathrm{Na} / \mathrm{Hg}+2 \mathrm{H}_{2} \mathrm{O} \rightarrow 2 \mathrm{NaOH}+\mathrm{H}_{2}+2 \mathrm{Hg}$

Answer 2

Manufacture of sodium hydroxide by castner's process:

The castner's process follows electrolysis of aqueous solution of NaCl to manufacture sodium hydroxide.

Explanation:

Mercury is used as cathode and titanium is used as anode.

When electric current is flowed through the electrode, positive and negative ions are produced.

The ionisation of sodium chloride is given as:

2 \mathrm{NaCl} \rightarrow 2 \mathrm{Na}^{+}+2 \mathrm{Cl}^{-}2NaCl→2Na

+

+2Cl

−

The reaction at cathode:

2 \mathrm{Na}^{+}+2 \mathrm{e}^{-} \rightarrow 2 \mathrm{Na}2Na

+

+2e

−

→2Na

The reaction at anode:

2 \mathrm{Cl}^{-} \rightarrow \mathrm{Cl}_{2}+2 \mathrm{e}^{-}2Cl

−

→Cl

2

+2e

−

The mercury has sodium, when it is treated with water, it produces NaOH. It is formed as solid.

2 \mathrm{Na} / \mathrm{Hg}+2 \mathrm{H}_{2} \mathrm{O} \rightarrow 2 \mathrm{NaOH}+\mathrm{H}_{2}+2 \mathrm{Hg}2Na/Hg+2H

2

O→2NaOH+H

2

+2Hg