Question

In one of the industrial processes for manufacture of sodium hydroxide, a gas X is formed as by-product. The gas X reacts with dry slaked lime to give a compound Y which is used as a bleaching agent in chemical industry. Identify X and Y giving the chemical equation of the reactions involved.

Answer 1

In the manufacturing of sodium hydroxide, hydrogen gas and chlorine gas (X) are formed as by-products. Chlorine gas reacts with dry slaked lime to give bleaching powder, a bleaching agent. Thus, X is chlorine gas $({\text{Cl}}_2$) gas.

Y is calcium oxychloride or bleaching powder ${\text{CaOCl}}_2$.

The equation for the preparation of sodium hydroxide is:

$\text{2NaCl (aq)}+2{\text{H}}_2\text{O (l)}\stackrel{\text{Heat}}{\to }2\text{NaOH (aq)}+{\text{Cl}}_2\text{(g)}+{\text{H}}_2\text{(g)}$

${\text{Cl}}_2\text{(g)}+{\text{Ca(OH)}}_2\text{(s)}\to {\text{CaOCl}}_2\text{(aq)}+{\text{H}}_2\text{O(l)}$