Question

With the help of a labelled diagram, describe the method of separating ammonium chloride from a mixture of ammonium chloride and common salt. Mention the difference in the properties of ammonium chloride and sodium chloride which has made this separation possible.

Answer 1

Fig., Separation of mixture of common salt and ammonium chloride by sublimation.

Sublimation is a method used for separating ammonium chloride from a mixture of ammonium chloride and common salt.

The procedure of separation is as follows:
• Mixture of common salt and ammonium chloride is taken in a china dish.
• This mixture is then kept on a burner.
• The china dish is covered with an inverted glass funnel.
• A loose cotton plug is placed over the open end of the funnel to prevent vapours from escaping.
• Mixture of common salt and ammonium chloride is then heated.
• Vapours of ammonium chloride are formed. These vapours, on rising, get condensed after coming in contact with the cold inner walls of the funnel.
• A white solid of pure ammonium chloride is obtained.
• Common salt does not change into vapours. So, it remains in the china dish.

This separation of ammonium chloride and common salt has been made possible by the difference in the properties of ammonium chloride and common salt. Ammonium chloride has a property to sublime, i.e., to get converted directly from solid to vapour state. However, common salt lacks this property. Also, ammonium chloride is a volatile substance, whereas common salt is nonvolatile in nature.