A product with a low boiling point is associated with which vapor characteristic?

• A. High vapor pressure
• B. High vapor density
• C. Low vapor pressure
• D. Low vapor density

Answer: (A)

A product with a low boiling point is highly volatile, which means it readily forms vapor at room temperature. This greater tendency to vaporize shows up as a high vapor pressure—it's the pressure the vapor exerts in equilibrium with the liquid. So, at a given temperature, a substance that boils easily has a higher vapor pressure. Vapor density (how heavy the vapor is relative to air) depends on molecular weight and isn’t determined by boiling point in the same way, and low vapor pressure would imply the opposite of what a low boiling point indicates.