Question

Ethanol is separated from water by:
A) Crystallisation
B) Chromatography
C) Fractional distillation
D) Adding methyl alcohol

Answer 1

Separation techniques are employed in mixtures depending upon their physical properties. This includes differences in boiling point, melting point etc. Fractional distillation is a very useful technique that can be employed here.

Complete step by step answer:
We know that water and ethanol mix to form a solution. The mixing of these compounds is an exothermic reaction and an adequate amount of heat is released during the process. The process is exothermic because of the difference in the size of the molecules of each component. We know that one component dissolves in another only if there is enough space between the particles of the other.
We know that the boiling point of water is ${\text{373 K}}$ and the boiling point of ethanol is ${\text{351}}{\text{.37 K}}$.Distillation is the common technique employed to separate mixtures having components who differ in their boiling points. But normal distillation is used only when there is sufficient difference in the boiling points of the components of the mixture. Here we can see that ethanol and water have only a small difference in their boiling points and it will be difficult to separate them using normal distillation.
Here we are using the technique called fractional distillation. This technique uses a fractionating column in the distillation apparatus so that the components do not get mixed up and can be collected separately from different parts of the fractionating column. Here the components are heated and their vapours condense at different temperatures in the column.

So, the correct answer is Option C .

Additional Information:
Ethanol is more volatile than water. So, it boils off first in the fractionating column and as it rises up, it gets condensed and gets collected in a separate beaker. The water after boiling gets condensed and then stays in the apparatus.

Note: Distillation is the common technique used to separate mixtures having components which show difference in their boiling points. There are different types of distillation like extractive distillation, normal distillation, fractional distillation etc.