Principles Related to Practical Chemistry

The technique used for purification of steam volatile water immiscible substances is :

1. Fractional distillation
2. Distillation
3. Fractional distillation under reduced pressure
4. Steam distillation

Answer

(4) Steam distillation

Solution

In steam distillation the mixture boils when pwater + pcompound = atmospheric pressure, i.e. below 373 K.

⇒ a steam-volatile, water-immiscible compound (e.g. aniline) distils with water without decomposing ⇒ (D) is correct

(A): fractional distillation – miscible liquids with close boiling points ⇒ (A) is not correct

(B): distillation – liquids with very different boiling points or non-volatile impurities ⇒ (B) is not correct

(C): distillation under reduced pressure – liquids that decompose at their boiling points ⇒ (C) is not correct

Answer: (4)