Henry’s Law

Sg = kPg

C= σ p

where

•Sg  (C) is the solubility of the gas;

•k  (σ ) is the Henry’s law constant for that gas in that solvent;

•Pg is the partial pressure of the gas above the liquid.

Works best for dilute solutions of gases that don’t interact with solvent

Example: CO2 has a Henry's law constant of 1.64x103 atm.

What is the mole fraction of CO2 dissolved in water when the pressure of CO2 above the solution is 1.35atm?

At pressure of few atmosphere or less, solubility of gas solute follows Henry Law which states that the amount of solute gas dissolved in solution is directly proportional to the amount of pressure above the solution.

  c = k P

c = solubility of the gas (M)

k = Henry’s Law Constant

P = partial pressure of gas

Henry’s Law Constants (25°C), k

N2  8.42 •10-7 M/mmHg

O2  1.66 •10-6 M/mmHg

CO2         4.48•10-5 M/mmHg