Question

Explain how you would separate a solid mixture of sand and salt using any of the following methods either distillation, chromatography, or crystallization.

Answer 1

Among Distillation, Chromatography and Crystallization methods, crystallization is the best method to separate salt from sand.

Let me explain first why Distillation and chromatography is bad choice for the separation

Distillation: Mixture of sand and salt will be heated above boiling point (above boiling point salt will become vapour) of salt and then condensing the vapour of salt will give pure salt. But the drawback is mostly salts will have boiling points above 1000 ^oC, therefore heating above 1000 ^oC is not that easy.

Chromatography: Adsorbent used for chromatography is not economical and separation of ionic compounds like salts are very difficult in chromatography (elution rate is very low)

Crystallization: to the mixture of sand and salt add minimum amount of water and stir to dissolve salt (sand will not dissolve in water). Filter the solution to remove all sand particles now the filtrate (water solution) contains only salt (free from sand). Then slowly evaporate water by boiling, once the water solution is more concentrated cool the solution to obtain the crystals of pure salt (or just leave it open in room temperature this will grow crystals slowly). Now pure form of salt crystals can be collected by filtration.