Partial pressure

Effect of temperature

Partial pressure decreases as temperature decreases.

When temperature decreases
--> kinetic energy of the molecules decreases
--> less likely to overcome Van der Waal forces
--> stay in solution more
--> less partial pressure

Dalton's law of partial pressures

In a mixture of gases, the pressure exerted by each gas is the same as that which it would exert if it alone occupied the container.

Henry's Law

At a particular temperature, the amount of a given gas dissolved in a given liquid is directly proportional to the partial pressure of the gas in equilibrium at the surface of the liquid.

• Describes the solution of gases in liquids with which they do not react.
  --> e.g. doesn't apply to O2 in blood
• Doesn't apply to vapours which are infinitely miscible with the solvent
  --> e.g. ether in oil

Thus,

• Dissolved gas = partial pressure x solubility coefficient