Question

In the process of separation of ammonium chloride from salt, ammonium chloride molecule____.
A ) evaporate
B ) sublime
C ) crystallize
D ) all of these

Answer 1

Hint: Volatile compounds undergo a process of sublimation. Non volatile compounds do not undergo sublimation. Sublimation is a process in which a solid is directly converted to vapours (gas phase) without entering liquid phase.

Complete answer:
Ammonium chloride undergoes sublimation whereas salt does not undergo sublimation.
Sublimation is a process which helps separation of salt and ammonium chloride. Common salt is sodium chloride. A mixture of salt and ammonium chloride is heated. Ammonium chloride upon heating undergoes sublimation. The phase of ammonium chloride changes from solid to gas. Liquid phase is not obtained when ammonium chloride solid is obtained. The vapors of ammonium chloride are collected, and condensed. When hot vapors of ammonium chloride come into contact with cold surfaces (such as the lid of the container) they lose heat energy. Due to cooling of vapours, they condense to give back solid ammonium chloride. This condensed ammonium chloride solid is deposited on the lid from where it can be collected. Salt remains behind in the container in which the mixture was heated. In this way, salt and ammonium chloride are separated.
Additional Information Crystallization is the process by which a solid dissolved in a solution is precipitated in the form of crystals. Evaporation is a process in which a liquid changes to a gas at room temperature or any other temperature upto the boiling point.

Note: Technique of sublimation is used to separate two components from a mixture. The condition of the separation by sublimation is that one of the two compounds to be separated should undergo sublimation. If neither compound undergoes sublimation or if both compounds sublime, then the mixture cannot be separated by this method.