Question

A mixture of benzene and aniline can be separated by:
A. Hot water
B. Dil. HCl
C. Dil. NaOH
D. Alcohol

Answer 1

Hint: Benzene is the cyclic compound of the formula \[{{\rm{C}}_{\rm{6}}}{{\rm{H}}_{\rm{6}}}\] . Aniline is also a substituted benzene compound, where, one hydrogen atom of benzene ring is replaced by the amine group, that is, \[{\rm{N}}{{\rm{H}}_{\rm{2}}}\] group. So, the formula of aniline is \[{{\rm{C}}_{\rm{6}}}{{\rm{H}}_5}{\rm{N}}{{\rm{H}}_{\rm{2}}}\].

Complete Step by Step Solution:
Let’s understand which reagent can separate a mixture of benzene and aniline.
The compound aniline possesses the character of weak base. When it is added to dilute hydrochloric acid (HCl), the formation of aniline hydrochloride occurs. The formed product aniline hydrochloride is a precipitate of black colour.

The chemical reaction is as follows:
\[{{\rm{C}}_{\rm{6}}}{{\rm{H}}_{\rm{5}}}{\rm{N}}{{\rm{H}}_{\rm{2}}} + {\rm{Dil}}{\rm{.}}\,{\rm{HCl}} \to {{\rm{C}}_{\rm{6}}}{{\rm{H}}_{\rm{5}}}{\rm{N}}{{\rm{H}}_{\rm{2}}} \cdot {\rm{HCl(Black}}\,{\rm{ppt}}{\rm{.)}}\]
But, Benzene does not undergo any reaction with dilute HCl. Therefore, both the compounds such as benzene and aniline are separated by reacting them with dilute hydrochloric acid.
Hence, the correct answer is option B, i.e., Dil. HCl.

Additional Information: Benzene is a chemical of no colour. It possesses light-yellow colour at room temperature. Primarily, It is used in the form of solvent in the chemical industries. In pharmaceutical industries, it is useful in the form of a starting material. The production of benzene is both manmade and natural.

Note: When a mixture of benzene and aniline is mixed with dilute HCl in a separating funnel, the separation of two layers takes place. When the non-aqueous layer undergoes distillation at 208 degrees results in the formation of benzene. The evaporation of the aqueous layer to dryness and then distilled with KOH gives pure aniline at a distillate.