Question
Explain, why an organic liquid vaporises at a temperature below its boiling point in its steam distillation?
Solution
The essential condition for a liquid to boil is that its vapour pressure should be equal to the external pressure. In steam distillation, the liquid boils when the sum of vapour pressure due to the organic liquid (p1) and water (p2) become equal to the atmospheric pressure (p) i .e. P = P1 + P2.
Since p1 is lower than p, the organic liquid vaporises at low temperature than its boiling point.
