Question

Separate pure ammonium chloride when it contains potassium chloride as a impurity

Answer 1

A mixture of ammonium chloride and potassium chloride can be separated using the process of sublimation. You must also note that both these substances are sublimable.
This technique is quite feasible in this case as the sublimable temperatures of ammonium and potassium chloride differ widely. Between the two, ammonium chloride has lower sublimable temperatures. Therefore, it sublimes first followed by potassium chloride.