Question

Question 12.28 Explain, why an organic liquid vaporises at a temperature below its boiling point in its steam distillation?

Class XI Organic Chemistry : Some Basic Principles and Techniques Page 363

Answer 1

Hi

Here is your answer,

In steam distillation the mixture consisting of the organic liquid and water boils when the sum of the vapour pressure of the organic liquid (p₁) and that of water (p₂) becomes equal to the atmospheric pressure (p) p = p₁ + p₂

Since, p₁ is lower then p, the organic liquid vaporises at lower temperature then its boiling point.

Answer 2

In steam distillation , the mixture consisting of the organic liquid and water boils at the temperature when the sun of the vapor pressure of the liquid (Pl) and that of water pressure ( Pw) becomes equal to the atmospheric pressure e.g., P = Pl + Pw
since the vapor pressure of water around the boiling point of the mixture is quite high and that of liquid is quite low ( 10 - 15mm), therefore , the organic liquid at a pressure much lower than the atmospheric pressure.

in other words , we can say that the organic liquid vaporize at a temperature much lower than its normal boiling point.