Answer to Question #31616 in Physical Chemistry for arindam roy

Question

why mixture of ethyl alcohol and water is an azeotropic mixture ??
why azeotropism occurs ??

Answer 1

An azeotrope is a mixture of two or more liquids in such a way that its components cannot be altered by simple distillation.
Ethanol forms a constant-boiling mixture (azeotrope (95% ethanol and 5% water). The boiling point of azeotropic mixture is 78.15°C. It is below that of pure ethanol, that’s why absolute ethanol cannot be obtained by simple distillation.

The azeotrope occurs when interaction between molucules is stronger than dipole-dipole forces or London dispersion. In the case of ethyl alcohol and water azeotrope hydrogen bonds are very, strong and hard to break.. So you can never completely break all of their bonds.