Henry’s Law

Gas in liquid Solution:

Gases are soluble in liquid to different extents. e.g., solubility of hydrochloric acid gas in water is more than the solubility of oxygen in water. The extent to which a gas dissolves in a liquid depends upon-

1)  Nature of gas and liquid: Solubility of non-polar bromine is more in non-polar solvents like CCI₄, CS₂, etc than in polar water.

2) Temperature: Solubility of a gas in a liquid decrease with the increase in temperature.

3) Pressure: Solubility of a gas in a liquid increase with increase in pressure of the gas above the solution.
Henry’s Law: At constant temperature, the solubility of a gas is directly proportional to the pressure at which it is dissolved. If m is the amount of gas and p is the pressure of gas in equilibrium with the solution, then according to Henry’s Law,

m α p

Or, m= K_H p

Where, K_H = Proportionality constant, called Henry’s constant,

m = amount of gas

p = pressure of gas

Limitation of Henry’s Law: Henry’s Law is valid only under following conditions:

1. The pressure and temperature of gas should not be very high.
2. The gas should not undergo any chemical reaction with solvents
3. The gas should not undergo dissociation in solution