The quantitative relation of pressure effect on solubility of gases was given by Henry, which is called Henry Law.
According to Henry's law, the solubility of a gas at a constant temperature is proportional to the pressure of that gas.
Therefore m ∝ P
or m = kP
Here is
m = amount of dissolved gas
P = gas pressure in equilibrium
k = proportionality constant.
If solubility is expressed in mole fraction of a gas in solution, then
According to Henry's law, the partial pressure (p) of a gas in its vapor state is proportional to the mole fraction (X) of gas in that solution.
ie p ∝ Xɢᴀs
either p = Kₕ Xɢᴀs
Here K is called Henry's constant.
If a graph is drawn between the partial pressure (p) and the mole fraction (X) of a gas, a straight line is obtained whose slope represents Kₕ.