Question

Potassium nitrate can be recovered from its solution from its solution by evaporation but ammonium chloride cannot. explain

Answer 1

This is because when a solution of potassium nitrate is heated, the water will evaporate and the potassium nitrate will crystallize forming potassium nitrate crystals.
However, for the ammonium chloride, when the solution is heated, the water evaporates and when the ammonium chloride gets heated as well, the ammonium chloride will sublimate. This will make it impossible for the separation to take place as the gaseous ammonium chloride will just mix with the water vapor.