A student purchases common salt from the market which is contaminated with ammonium chloride (NH4Cl ). Identify the technique that he should adopt to obtain pure NaCl.
Sublimation
Ammonium chloride is a substance which directly converts to vapour upon heating, without going through the liquid state. This process is called sublimation. The vapours can be collected and condensed into a separate flask. On the other hand, NaCl does not get vaporised at that temperature and can be separated easily.