Question

Assertion : In general within a family, boiling point increases with increasing molecular mass.

Reason : The larger a molecule, the more likely its electron cloud is to polarize and establish dispersion intermolecular forces.

• A. Assertion and Reason are correct and Assertion is the correct explanation of Reason.
• B. Both the Assertion and Reason are correct and Reason is not the correct explanation of Assertion.
• C. Assertion is correct but Reason is not correct.
• D. Assertion is not correct but Reason is correct.
• E. Both the Assertion and Reason are not correct.

Answer 1

The correct option is A Assertion and Reason are correct and Assertion is the correct explanation of Reason.

Larger and heavier molecules have stronger London dispersion forces. When you look at the valence electrons in the larger molecule, they are farther from the nucleus than the electrons in the smaller molecules. As a result, they are not as tightly held so what happens is they can easily form temporary dipoles called London forces which produce that force of attraction. So this increase in intermolecular attraction with increasing size of a molecule is reflected by an increase in boiling points. Remember boiling points increase as the forces of attraction between molecules increase.