Question

To separate ammonium chloride from common salt, we use:

(A) Filtration

(B) Sedimentation

(C) Sieving

(D) Sublimation

Answer 1

Hint: It is the process in which a solid substance is directly converted to the gaseous phase and vice versa without coming to the intermediate liquid state. It is a special type of phase transition. The most common examples are the formation of dry ice and decomposition of camphor.

Complete step by step answer:

- We use the sublimation process to separate ammonium chloride from common salt.

- It is the easiest way to do the separation.

- The common salt, sodium chloride is not volatile whereas ammonium chloride is volatile

> The procedure is as follows:

1) A mixture of salt and ammonium chloride is taken in a China dish.

2) Now, a funnel is taken and placed inverted over the dish in such a way that the dish is covered fully with the mixture.

3) It is kept on a stand and heated with Bunsen burner.

After some time, it is noticed ammonium chloride is stuck on the walls of the funnel and salt remains there in the funnel.

In this way, they are separated easily.

So, the correct option is D.

Note: The separation of ammonium chloride from common salt by sublimation involves both physical and chemical change.

It is a physical change when solid ammonium chloride is converted to gaseous phase due to sublimation and a chemical change when gaseous ammonium chloride is decomposed into ammonia and hydrochloric acid at the sublimation temperature.

\[N{{H}_{4}}Cl(s)\xrightarrow{\text{sublimation}}N{{H}_{4}}Cl(g)\to N{{H}_{3}}+HCl\]