Question

Explain giving reasons;

What happens when the crystals of washing soda are exposed to air?

Answer 1

1. When crystals of washing soda are exposed to air it undergoes efflorescence through which it loses its nine water molecules of crystallisation.
2. Due to the loss of water molecules, washing soda turns into white powder called washing powder.

Reaction involving in this process:

$\underset{\mathrm{Washing}\mathrm{soda}}{{\mathrm{Na}}_2{\mathrm{CO}}_3·10{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)}\stackrel{\mathrm{air}}{\to }\underset{(\mathrm{White}\mathrm{powder})}{\underset{\mathrm{Washing}\mathrm{powder}}{{\mathrm{Na}}_2{\mathrm{CO}}_3·{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)}}+\underset{\mathrm{Water}}{9{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}$

1. Efflorescence refers to a process through which any substance loses its water of crystallization for moisture.
2. Also, here washing soda is called an efflorescent, which loses its moisture when exposed to air.

Therefore, when crystals of washing soda are exposed to air, white powder called washing powder is formed.