Ammonium chloride is separated from a mixture of sodium chloride and ammonium chloride by the process of _____.
A. Crystallization
B. Filtration
C. Sublimation
D. All of these

Hint: Ammonium chloride$(N{H_4})$ is a solid which on heating gives a dissociation reaction. Ammonium chloride dissociates to give ammonia $(N{H_3})$ and hydrochloric acid (HCl).

Complete step by step answer:
Crystallization is a process of the formation of crystals from the solution or any compound which has been melted. In this process, the solution is concentrated to a supersaturated state to form solid particles known as crystals.
Filtration is a process where the mixture of solid and liquid is separated using a filter medium. The filter medium allows the liquid to pass through it but not the solid compound.
Sublimation is a process where a solid compound on heating changes its state from solid to gaseous.
In the mixture of ammonium chloride and sodium chloride, both the compounds are in solid form.
When ammonium chloride is heated it gets sublimated and produces ammonia gas and hydrochloric gas.
The reaction is shown below.
$N{H_4}Cl \to N{H_3} + HCl$
When sodium chloride is heated, it starts melting and on further heating, the liquid of ammonium chloride starts to boil.
Thus, when the mixture of ammonium chloride and sodium chloride is heated, ammonium chloride sublimes to give gas which on condensing is separated in another beaker and the liquid sodium chloride remains in the beaker.
Thus, ammonium chloride is separated from a mixture of sodium chloride and ammonium chloride by the process of sublimation.

Therefore, the correct option is C.

Note:
In the separation of ammonium chloride and sodium chloride basically two processes take place one is sublimation and the other condensation. In the condensation process, the gas changes its state to liquid.