Question

A chromatography column, packed with silica gel as a stationary phase, was used to separate a mixture of compounds consisting of (A) benzanilide, (B) aniline and (C) acetophenone. When the column is eluted with a mixture of solvents, hexane : ethyl acetate (20:80), the sequence of obtained compounds is:

• A. (B), (A) and (C)
• B. (C), (A) and (B)
• C. (B), (C) and (A)
• D. (A), (B) and (C)

Answer 1

The correct option is B

(C), (A) and (B)

Column chromatography:

• Column chromatography is used to separate a single chemical from a mixture of substances.
• In this question, we have a mixture of three substances (A) benzanilide (B) aniline (C) acetophenone.
• Here a mixture of two solvents is used to separate the mixture of three substance. In this case, hexane (${\mathrm{C}}_6{\mathrm{H}}_{12}$)as well as ethyl acetate(${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{COOCH}}_3$) is used in the ratio of $20:80$.
• Hexane is a non-polar solvent with a composition of only $20\%$ and ethyl acetate is a polar solvent with a composition of $80\%$. When compared to polar solvents, nonpolar substances have a lower quality.
• As a result, the polar compounds in a mixture that are more polar will separate out first with the polar solvent.
• As a result, acetophenone${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{COCH}}_3$ is more polar among the given compounds so, it will separate out first.
• After that benzanilide (${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{NHCOC}}_6{\mathrm{H}}_5$) which is more polar than aniline (${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{NH}}_2$).

Hence, the correct answer will be (C), (A) and (B).