ACS Chemistry Practice Exam 2026 – The All-in-One Guide to Exam Success!

A low vapor pressure of a liquid indicates that the liquid has a lower tendency to vaporize. This is typically associated with stronger intermolecular forces present in the liquid. When there are strong intermolecular forces, the molecules are held together more tightly, making it more difficult for them to escape into the vapor phase, which results in lower vapor pressure.

Additionally, a liquid with low vapor pressure generally requires more energy to vaporize, reflecting a higher heat of vaporization. The heat of vaporization is the amount of energy required to convert a unit quantity of liquid into a gas at a constant temperature and pressure. Therefore, a high value of heat of vaporization correlates with a low vapor pressure, as it quantifies the energy necessary to overcome the intermolecular attractions effectively.

In summary, the relationship between low vapor pressure and higher heat of vaporization is rooted in the strength of intermolecular forces, which dictate both the tendency to vaporize and the energy required to do so.