Question

Two liquids (P) and (Q) can be separated by the method of fractional distillation. The boiling points of P and Q are _____ and _______ respectively.

• A. $329\mathrm{K}\mathrm{and}332\mathrm{K}$
• B. $329\mathrm{K}\mathrm{and}354\mathrm{K}$
• C. $329\mathrm{K}\mathrm{and}373\mathrm{K}$
• D. $329\mathrm{K}\mathrm{and}473\mathrm{K}$

Answer 1

The correct option is A

$329\mathrm{K}\mathrm{and}332\mathrm{K}$

Explanation for correct option:

A. $329\mathrm{K}\mathrm{and}332\mathrm{K}$

Fractional distillation:

• “To separate a mixture of two or more miscible liquids for which the difference in boiling points is less than $25\mathrm{K}$, the fractional distillation process is used.”
• Fractional distillation involves the separation of two miscible liquids.
• For example mixture of ethanol and water can be separated by using fractional distillation.
• A simple fractionating column consists of a tube packed with glass beads. The beads provide a surface for the vapors to cool and condense repeatedly."
• The apparatus for fractional distillation is given below:

Thus, the boiling points of P and Q are $329\mathrm{K}\mathrm{and}332\mathrm{K}$ respectively.

Explanation for incorrect options:

The difference in the boiling points of liquids P and Q is less than $25\mathrm{K}$ i.e. $\left(329\mathrm{K}-332\mathrm{K}=3\mathrm{K}\right)$ Thus options B, C, and D are incorrect.

Hence, the correct option is A i.e. $329\mathrm{K}\mathrm{and}332\mathrm{K}$.