Relation between Structure and Vapor Pressure

[Patrick Blankenberg]

One of the questions on the homework asks us to analyze relative vapor pressure of a molecule based on its lewis structure. What exactly is vapor pressure and how can the lewis structure of a molecule impact it?

[Sono Fukushima 2D]

Vapor pressure related to the energy required for a substance to vaporize, or evaporate. The higher the vapor pressure, the lower the boiling point. Since evaporation occurs when bonds between molecules are broken to form a gas, weaker bonds require less energy or heat to be broken compared to stronger bonds. Therefore stronger bonds have lower vapor pressure, and the bond strengths can be compared through comparison of Lewis structures.

[Daniel P 3J]

Vapor pressure is the pressure created by the vapor (gas) of a liquid in a closed container. The Lewis structure of a molecule affects its vapor pressure because it shows how atoms are bonded in the molecule. Stronger bonds and intermolecular forces (like hydrogen bonding or Van der Waals forces) in a molecule make it harder for the liquid to turn into gas, resulting in lower vapor pressure. Conversely, weaker bonds and forces lead to higher vapor pressure.