Question

You have a mixture of three liquids A, B and C. there is a large difference in the boiling points of A and rest of the two liquids i.e. B and C. Boiling point of liquids B and C are quite close. Liquid A boils at a higher temperature than B and C and boiling point of B is lower than C. How will you separate the components of the mixture. Draw a diagram showing set up of the apparatus for the process.

Answer 1

Separation of liquid A from mixture of liquids A, B and
C.

• Simple distillation is an important method for separation of the liquids having sufficient difference in their boiling points.
• The boiling of liquid A is much higher than liquids B and C. So, liquids A can be separated from liquids B and C by simple distillation method .
• Liquids having different boiling points vapourise at different temperatures. The vapours are cooled, and the liquids so formed are collected separately.
• Since, liquid B and C have lower boiling point than liquid A and there is large difference in their boiling point with respect to liquid A. So, liquid B and C can be separated easily from liquid A.

Separation of liquids B and C.

• If the difference in boiling points of two liquids is not much, simple distillation cannot be used to separate them. The vapours of such liquids are formed within the same temperature range and are condensed simultaneously. The technique of fractional distillation is used in such cases.
• The boiling points of remaining two liquids i.e. B and C are quite close. So, fractional distillation technique will be used to separate them.
• In this technique, vapours of a liquid mixture are passed through a fractionating column before condensation. The fractionating column is fitted over the mouth of the round bottom flask.