Explain the sublimation with help of a practical example?
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Some solid have a tendency to submine on heating i.e. they convert directly from solid to gaseous / vapour phase on heating without passing through the liquid phase. A mixture containing such solid with any other solid can be separated by sublimation . examples of solids that sublime are camphor, ammonium chloride, naphthalene, iodine , anthracene, etc . hence sublimation is used to separate such mixtures that contains a sublimable volatile components from a non sublimable impurity.
For example : A mixture of common salt and ammonium chloride can be separated by sublimation . The mixture is heated in a china dish , above which , inverted funnel steam of which has closed with cotton has been placed. The vapours of ammonium chloride become cool and solidify when coming in contact with the walls of the funnel and thus solid ammonium chloride is separated . Common salt is left in the china dish.
The best example of sublimation is dry ice which is a frozen form of carbon dioxide.
When dry ice gets exposed to air, dry ice directly changes its phase from solid-state to gaseous state which is visible as fog.
At a temperature of 176F naphthalene sublimes to form vapours.