Question

Which of the following statement(s) is/are correct?

• A. Distillation is used to seperate two mixtures based on their difference in relative densities.
• B. In fractional distillation vapours of the liquid mixture are passed through a fractionating column before condensation.
• C. Distillation is used to seperate two mixtures based on their difference in their boiling points.
• D. In fractional distillation vapours of the liquid mixture are passed through a fractionating column after condensation.

Answer 1

Answer: (B), (C)

The correct options are
B In fractional distillation vapours of the liquid mixture are passed through a fractionating column before condensation.
C Distillation is used to seperate two mixtures based on their difference in their boiling points.

Distillation :
Used to separate volatile liquids from non-volatile impurities.Used to separate liquids having sufficient difference in their boiling points
Simple distillation :
This method is used if the difference in boiling points of the two liquids is large enough $(>{30}^{\circ }C)$ or to separate volatile compounds from non-volatile impurities.
Example : Water-Acetone mixture can be seperated by simple distillation.

Fractional distillation :
This method is used if the difference in boiling points of the two liquids is not much, and simple distillation can't be used to separate them.
In fractional distillation, vapours of the liquid mixture are passed through a fractionating column before condensation.
Vapours rising up in the column become richer in the more volatile (lower boiling point) component, as the less volatile component loses heat and gets condensed.
The vapors of the more volatile component rising up through the column are then condensed and collected in a separate flask.