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ChemistryEdu Logo Solution | Vapour Pressure of Liquid Solution#

Vapour Pressure#

  • The pressure exerted by vapours of a liquid over its liquid surface when the liquid and vapours are in equilibrium is known as vapour pressure.
  • Equilibrium means the state where rate of vaporization is equal to rate of condensation.

Vapour Pressure image from wikipedia

Image Credit: https://en.wikipedia.org/wiki/Vapor_pressure

Factors affecting vapour pressure#

  1. Nature of liquid:
    • The liquid having strong attraction forces between its molecules will have lower vapour pressure as compared to other liquids.
    • Example: water has lower vapour pressure as compared to alcohol due to this reason.
  2. Temperature:
    • On increasing temperature, vapour pressure of liquid will increase and vice-versa.
  3. Surface Area of liquid:
    • Vapour pressure increases with increase in surface area of liquid and vice-versa.
  4. Purity of solution:
    • Vapour pressure of pure liquid will always be greater than the vapour pressure of its solution with a non-volatile solid.
    • For example, vapour pressure of pure water is greater than (water + sugar) solution.