A mixture of sodium chloride (salt) and ammonium chloride can be separated by

The correct answer is A, sublimation. Ammonium chloride sublimes: on heating, it changes directly from a solid into vapour without melting, and the vapour turns back into solid on a cool surface. Sodium chloride does not sublime and stays behind in the dish. So if the mixture is heated in a china dish covered with an inverted funnel, the ammonium chloride collects on the cooler walls of the funnel and the common salt remains below. Other substances separated the same way include camphor, naphthalene, iodine and anthracene. Option B is wrong because both salts dissolve in water, and filtration only separates an insoluble solid from a liquid. Option C is wrong because chromatography separates components that dissolve in the same solvent but move at different rates, such as the dyes in ink. Option D is wrong because distillation separates miscible liquids, or a liquid from a dissolved solid, by their boiling points. Exam tip: salt and ammonium chloride, sublimation; salt and sand, dissolving and filtration; dyes in ink, chromatography.