Question

Water and alcohol can be separated from a mixture by:
a) Fractional distillation
b) Sublimation
c) Decantation
d) Evaporation

Answer 1

Water and alcohol are separated on the basis of difference in their boiling point. Water and alcohol both have different boiling points.

Complete Solution:
- During the process of fractional distillation, the mixture is heated and one of the liquids evaporates before the other. This is based on the principle of evaporation. Both the compounds have different boiling points.
- Ethanol boils at a low temperature of 78.5 degree centigrade and water boils at the temperature of 100 degree centigrade. The alcohol evaporates while most of the water remains in the liquid state.
Hence, the chemical compounds are separated by heating them to a temperature at which one or more fractions of the mixture will vaporize. The compounds with lower boiling point vaporize first.

So, the correct answer is “Option A”.

Note: The liquid air also undergoes the process of fractional distillation. It is generally used for the difference in boiling point of the elements of the air. The air in the earth atmosphere consists of the nitrogen, argon, oxygen, carbon dioxide and many other gases. So, to basically separate the sample of air into its primary components the air is cooled first and this process is further known as the fractional distillation of liquid air. Further an air separator unit is required which is not unlike a conventional distillation tube is used for purifying the water.