Question

Which of the following has the lowest boiling point?

• A. Butanol
• B. Propanol
• C. Ethanol
• D. Methanol

Hint:

The boiling point of alcohols increases as the size of the molecule increases, due to stronger intermolecular hydrogen bonding. Methanol, being the smallest, has the lowest boiling point.

Answer 1

The Correct Option is D

The boiling point of a substance depends on its molecular structure and intermolecular forces. Alcohols, such as butanol, propanol, ethanol, and methanol, have hydrogen bonding, which tends to increase their boiling points. However, the strength of these intermolecular forces also depends on the size of the molecule.
Step 1: Molecular Structure and Boiling Points - Methanol (CH3OH): Methanol is the smallest molecule in the list, with the least number of carbon atoms. It has hydrogen bonding, but because of its small size, the forces are not as strong as in the larger alcohols, resulting in the lowest boiling point. - Ethanol (C2H5OH): Ethanol is larger than methanol, so it has stronger intermolecular forces and a higher boiling point than methanol. - Propanol (C3H7OH): Propanol is larger than ethanol and thus has an even higher boiling point due to stronger hydrogen bonding. - Butanol (C4H9OH): Butanol is the largest molecule in this series and has the strongest intermolecular forces, leading to the highest boiling point.
Step 2: Conclusion Since methanol is the smallest molecule among the listed alcohols, it has the weakest intermolecular forces and the lowest boiling point. Thus, the correct answer is \( \boxed{\text{Methanol}} \).