Question

Arrange the following in the correct order of their boiling points: 

• A. I $>$ III $>$ II $>$ IV
• B. II $>$ I $>$ III $>$ IV
• C. III $>$ II $>$ I $>$ IV
• D. II $>$ III $>$ IV $>$ I

Hint:

Alcohols exhibit higher boiling points than alkanes due to hydrogen bonding. Among alcohols, larger molecules tend to have higher boiling points.

Answer 1

The Correct Option is D

The boiling points of substances depend on their molecular structure and intermolecular forces, particularly hydrogen bonding. - Ethanol (I: \(\text{C}_2\text{H}_5\text{OH}\)): Ethanol is a small alcohol with hydrogen bonding and has a relatively high boiling point due to the ability to form hydrogen bonds. - Propanol (II: \(\text{C}_3\text{H}_7\text{OH}\)): Propanol is larger than ethanol, but the additional carbon chain doesn't significantly increase the boiling point compared to ethanol. - Ethanol (\(III: \text{CH}_3\text{CH}_2\text{OH}\)): Ethanol is slightly smaller than propanol but still capable of hydrogen bonding, so it has a boiling point lower than that of propanol. - Butane (IV: \(\text{CH}_3\text{CH}_2\text{CH}_3\)): Butane, a non-polar molecule, has a significantly lower boiling point because it only experiences van der Waals forces, not hydrogen bonding. Hence, the correct order of boiling points is: \[ \text{II $>$ III $>$ IV $>$ I}. \]