Question

Aniline is separated from a mixture by:
(a)- Fractional crystallization
(b)- Fractional distillation
(c)- Vacuum distillation
(d)- Steam distillation

Answer 1

We know that aniline is a liquid and the process by which the mixture is separated by a process in which the principle is when the mixture is heated, both would exert vapor pressure independently and both will start to boil at a lower pressure than the actual boiling point of both the compounds.

Complete answer:
Aniline is an aromatic compound, in which an amine group is present on the benzene ring, and it is a liquid that is not miscible in water. So, we can separate the mixture of aniline and water by steam distillation. In steam distillation, the compounds that are purified are those compounds that are volatile in steam, insoluble in water, possess water pressure of about 10-15 mm Hg at 373 K, and contain non-volatile impurities.
It is based on the principle that there are some organic compounds that have a high boiling point and these compounds decompose before the boiling point, so we have to separate them before decomposing. When the aniline is mixed with the water and heated, it will exert vapor pressure independently and will be equal to the atmospheric pressure, this decreases the boiling point of the mixture and then it will start to boil at a lesser temperature. So, at this temperature aniline will not decompose and impurities will be left behind. Now, the vapors can be condensed and separated to collect the aniline.

Therefore, the correct answer is an option (d).

Note: The ratio in which the aniline and water are separated is 43: 717. Another organic compound that is separated from the steam distillation method is nitrobenzene, and its ratio is 1: 37.