Question

Sodium hydroxide or caustic soda is a useful industrial chemical and is manufactured by chlor-alkali process. In the process, a gas X is formed as the by-product. It reacts with slaked lime to give a compound Y which finds application as a bleaching agent for the clothes. Which is the main raw material for the process?

Answer 1

1. The Chlor-alkali process is the process that is used to manufacture chlorine $\left({\mathrm{Cl}}_2\right)$, hydrogen $\left({\mathrm{H}}_2\right)$, and sodium hydroxide (NaOH).
2. As we know that raw material is a basic material from which a product is made.
3. Concentrated sodium chloride $\mathrm{(}\mathrm{conc}\mathrm{.}\mathrm{NaCl}\mathrm{)}$ is also called brine is used as a raw material in the Chlor-alkali process as it decomposes to form sodium hydroxide$\left(\mathrm{NaOH}\right)$, hydrogen $\left({\mathrm{H}}_2\right)$ and then chlorine $\left({\mathrm{Cl}}_2\right)$ as a by-product.

Reaction involves:

$2\mathrm{NaCl}\left(\mathrm{aq}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\stackrel{}{\to }2\mathrm{NaOH}\left(\mathrm{aq}\right)+{\mathrm{Cl}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$

Thus, the main raw material used for this process is the solution of concentrated sodium chloride $\mathrm{(}\mathrm{conc}\mathrm{.}\mathrm{NaCl}\mathrm{)}$.