Why does a compound with a high vapor pressure boil at a lower temperature than a compound with a lower vapor pressure?
high vapor pressure: more molecules escaping the liquid phase creats a higher vapor concentration, and pressure.
P=(N/v)RT N/v is the vapor concentration of the substance
The higher the vapor pressure rating the more quickly the solution will volatilize so the lower the boiling point. Conversely, the lower the rate the more slowly it evaporates so the boiling point is higher.
A compound's vapor pressure is directly related to its boiling point. The vapor pressure of a substance refers to the pressure exerted by its vapor in equilibrium with its liquid phase at a specific temperature. The higher the vapor pressure, the more easily the substance evaporates.
When a compound with a high vapor pressure is heated, its molecules have enough kinetic energy to escape from the liquid phase and transition into the gas phase. This results in the substance boiling at a lower temperature because the vapor pressure of the liquid reaches the ambient pressure more quickly.
Conversely, a compound with a lower vapor pressure requires more energy input to overcome the intermolecular forces and transition into the gas phase. Therefore, it will have a higher boiling point because it needs to reach a higher temperature to generate enough vapor pressure to match the ambient pressure.
To understand the relationship between vapor pressure and boiling point, it is crucial to consider the intermolecular forces within the compound. Compounds with stronger intermolecular forces, such as hydrogen bonding or dipole-dipole interactions, generally have lower vapor pressures and higher boiling points compared to compounds with weaker intermolecular forces or non-polar compounds.
In summary, compounds with high vapor pressures boil at lower temperatures because their molecules evaporate more readily, whereas compounds with low vapor pressures require higher temperatures to generate enough vapor pressure for boiling.