Question

based on the information in the table above, which of the compounds has the highest boiling point, and why?
(a) butanal, because it can form intermolecular hydrogen bonds
(b) pentane, because it has the longest carbon chain
(c) pentane, because it has the most c - h bonds
(d) propanoic acid, because it can form intermolecular hydrogen bonds

Explanation:

Step1: Analyze intermolecular forces

Pentane has only London dispersion forces. Butanal has dipole - dipole forces (due to the carbonyl group). Propanoic acid can form intermolecular hydrogen bonds (due to the -COOH group). Hydrogen bonds are stronger than dipole - dipole and London dispersion forces.

Step2: Relate intermolecular forces to boiling point

Stronger intermolecular forces require more energy to break, resulting in a higher boiling point. Since propanoic acid has the strongest intermolecular forces (hydrogen bonds), it will have the highest boiling point among the three.

Answer:

D. Propanoic acid, because it can form intermolecular hydrogen bonds