Question

Aniline has high boiling point and high vapor pressure at $100{}^{0}C$ and is insoluble in water. Aniline is therefore separated by:
a.) Simple distillation
b.) Vacuum distillation
c.) Steam distillation
d.) Distillation under reduced pressure

Answer 1

Hint: Here we are having the mixture of aniline with water. Aniline’s boiling point is $184{}^{0}C$ and water’s boiling point is $100{}^{0}C$. As there is a large difference in boiling point that’s why distillation method will be used, also water and aniline are insoluble in each-other so steam distillation will be an effective method to separate them.

Complete Solution :
Simple distillation: This method is used to separate solvent from its solution when a solute of much higher boiling point than solvent is dissolved in it.

- Vacuum distillation: Vacuum distillation is the process of lowering the pressure in the column above the solvent to less than the vapor pressure of the mixture, creating a vacuum, and causing the elements with lower vapor pressures to evaporate off. It is used when the boiling point of the compound (or the solvent) is too high, in order to distill the compound (or the solvent off) without significant decomposition and also to save energy.

- Steam distillation: In steam distillation, the immiscible mixture is heated to boiling, causing the distillation of water. This method is generally used when a compound immiscible with water has a very higher boiling point than water. This means that on heating water evaporates first and steam travels upwards to a condenser, which then condenses the steam to water so that it can be collected.
So to separate Aniline-water mixture steam distillation is the proper method.
So, the correct answer is “Option C”.

Additional Information:
For an immiscible mixture, boiling occurs at a much lower temperature than the boiling points of the individual components. As each individual component contributes independently, less heat is required to increase the total vapor pressure to the atmospheric pressure.

Note: In an immiscible mixture, where the components form a heterogeneous mixture, the vapor pressures of each component contribute independently to the total vapor pressure. Thus, the total vapor pressure is equal to the sum of the individual pure vapor pressures. In an immiscible mixture composed of two liquids, the total pressure is defined as the vapor pressure of the first liquid plus the vapor pressure of the second liquid.