Dalton’s Law

  • In a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases. Ptotal= P1+P2+….Pn
  • The partial pressure of a gas is the pressure exerted by that gas on its container independent of other gases.
  • Since each gas in a mixture is at the same temperature & is contained in the same volume Dalton’s law states that their individual partial pressures can be simply added to find the total
  • pressure in a container.
  • Pgas1= %total gas1 x Ptotal
  • Example- at standard barometric pressure (760 mm Hg) oxygen is ~21% of atmospheric air.
  • Therefore PO2= 0.21 x 760 mmHg = 160 mmHg


  1. http://en.wikipedia.org/wiki/Dalton%27s_law