Question

Fractional distillation is suitable for separation of miscible liquids with a boiling point difference of about 25 K or less. What part of fractional distillation apparatus makes it efficient and possess an advantage over a simple distillation process. Explain using a diagram.

Answer 1

The fractionating column is the most important part of the fractional distillation apparatus. This column is provided with some glass beads in it.
It helps to obstruct the upward movement of the vapours of the two liquids. The vapours of high boiling liquid get condensed earlier (at the lower level). The energy (latent heat) released helps to take the vapours of low boiling liquid to a height in the fractionating column. The advantages are as given below
(i) This method can separate the liquids with a boiling point difference about or less than 25 K.
(ii) During the process, both evaporation and condensation take place simultaneously.
(iii) A mixture (like petroleum) can also be separated by fractional distillation process which contains several components.