Vapor pressure is the pressure exerted by the vapor when a liquid or solid is in equilibrium with its vapor phase.
It’s a measure of a substance’s tendency to evaporate.
Factors Affecting Vapor Pressure:
Temperature:
Higher temperature increases vapor pressure because more particles have enough energy to escape into the vapor phase.
Nature of the Liquid:
Substances with weaker intermolecular forces have higher vapor pressures.
Dynamic Equilibrium:
In a closed container, when the rate of evaporation equals the rate of condensation, the vapor pressure stabilizes.
Example: A closed bottle of water eventually reaches a state where the water vapor in the air above the liquid exerts a constant pressure.
Importance:
Weather and Climate: Influences humidity and the formation of clouds.
Industrial Applications: Important in processes like distillation and refrigeration.
Safety: High vapor pressure substances can be more flammable or pose evaporation-related hazards.
Example:
At 25°C, water has a vapor pressure of about 23.8 mmHg.
If placed in a sealed container, water vapor will exert this pressure when equilibrium is reached.