Vapor pressure also called equilibrium vapor pressure is defined as the pressure exerted by a vaporin thermodynamic equilibrium with its condensed phases(solid or liquid) at a given temperature in a closed system.
Vapor pressure indicates the evaporation rate of a liquid.
A substance with a high vapor pressure at normal temperatures is called a volatile substance.
Factors affecting vapor pressure of a liquid:
Nature of liquid: The vapor pressure decreases with an increase in the value of intermolecular forces and when the value of intermolecular forces decreases, the vapor pressure of the liquid increases.
Boiling point of liquid: The boiling point of a liquid is inversely proportional to the vapor pressure. If the boiling point of a liquid is high then it will have a lower vapor pressure.
Effect of temperature: The kinetic energy of the molecules increases with an increase in temperature. Molecules having higher kinetic energy will leave the liquid surface more quickly and the vapor pressure will increase Hence, the temperature is directly proportional to the vapor pressure of a liquid.
Concentration of solute: The vapor pressure of the liquid decreases when a solute is added to a solvent. Therefore, the vapor pressure of pure solvent when compared to solute added solvent will have a higher magnitude.
The vapor pressure of a liquid depends upon its nature, boiling point, temperature, and solute concentration.
