Question

how are the vapor pressure and boiling point of alkynes affected as the chain length increases?
both vapor pressure and boiling point decrease.
both vapor pressure and boiling point increase.
vapor pressure increases, and boiling point decreases.
vapor pressure decreases, and boiling point increases.

Explanation:

As the chain - length of alkynes increases, the molecular mass and the strength of London - dispersion forces increase. Stronger intermolecular forces mean it is harder for molecules to escape into the vapor phase (lower vapor pressure) and more energy is required to separate the molecules to reach the boiling point (higher boiling point).

Answer:

D. Vapor pressure decreases, and boiling point increases