Among benzene, toluene, xylene, and acetone, which has the highest vapor pressure?

The correct answer is acetone because it has the highest vapor pressure among the compounds listed. Vapor pressure is a measure of a substance's tendency to evaporate; it reflects how readily a liquid can transform into vapor at a particular temperature.

Acetone is a small, polar, and relatively low-molecular-weight compound. Its molecular structure contributes to a lower boiling point compared to benzene, toluene, and xylene. Consequently, acetone's higher vapor pressure implies that it can more easily transition into the gaseous phase compared to the other substances. In contrast, benzene, toluene, and xylene have larger and more complex molecular structures, leading to stronger intermolecular forces (like Van der Waals forces) which reduces their vapor pressures relative to acetone.

Understanding these characteristics allows us to recognize why acetone exhibits a higher vapor pressure, making it more volatile than the other solvents listed.