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Why is it not possible to obtain pure ethanol by fractional distillation? What general name is given to binarymixtures which show deviation from Raoult's law and whose components cannot be separated by fractional distillation. How many types of such mixtures are there?
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Pure ethanol solution is an example of azeotropes. Such solution have same composition in liquid as well as in vapour phase and boils at a constant temperature. Due to constant composition it cannot be separated by fractional distillation.
There are two types of azotropes :
(i) Minimum boiling azeotropes: Solutions which show large positive deviation from Raoult's law form minimum boiling azeotropes at a specific composition, e.g., ethanol-water mixture.
(ii) Maximum boiling azeotropes : Solutions which show large negative deviation from Raoult's law form maximum boiling azeotropes. E.g., solution having composition. $68 \% \mathrm{HNO}_3$ and $32 \%$ water by mass.
There are two types of azotropes :
(i) Minimum boiling azeotropes: Solutions which show large positive deviation from Raoult's law form minimum boiling azeotropes at a specific composition, e.g., ethanol-water mixture.
(ii) Maximum boiling azeotropes : Solutions which show large negative deviation from Raoult's law form maximum boiling azeotropes. E.g., solution having composition. $68 \% \mathrm{HNO}_3$ and $32 \%$ water by mass.
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