Question

Which separation technique will you apply for the separation of the following mixture?

Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.

Answer 1

The separation technique applied for the separation of Ammonium chloride $\left({\mathrm{NH}}_4\mathrm{Cl}\right)$ from the mixture of Sodium chloride $\left(\mathrm{NaCl}\right)$ and ammonium chloride is sublimation.

Sublimation: The process of conversion of a substance from the solid state into gaseous state on heating directly without converting into liquid state.

• Example: Camphor, Iodine $\left({\mathrm{I}}_2\right)$, Naphthalene, Anthracene
• $\underset{(\mathrm{Ammonium}\mathrm{chloride})}{{\mathrm{NH}}_4\mathrm{Cl}\left(\mathrm{s}\right)}\underset{\mathrm{Cool}}{\overset{\mathrm{Heat}}{\rightleftarrows }}\underset{(\mathrm{Ammonium}\mathrm{chloride})}{{\mathrm{NH}}_4\mathrm{Cl}\left(\mathrm{g}\right)}$

Principle: Sublimable substance leaves the mixture on heating whereas non-sublimable substance is left behind.

When heated, ammonium chloride can undergo sublimation and collected in a cotton-plugged inverted funnel on cooling whereas sodium chloride does not undergo sublimation. As a result, ammonium chloride leaves the mixture when heated and sodium chloride is left behind.