We are familiar that gases are completely miscible with each other. Gases also dissolve in liquids and solids. For example, soda water contains carbon dioxide dissolved in water under high pressure. Oxygen is sufficiently soluble in water to allow the survival of aquatic life in lakes, rivers, and oceans. An example of the dissolution of gas in a solid is the solubility of hydrogen gas in palladium.

The solubility of a gas in a liquid is determined by several factors. In addition to the nature of the gas and the liquid, the solubility of the gas depends on the temperature and pressure of the system. The solubility of a gas in a liquid is governed by Henry’s law which states that the solubility of a gas in a liquid is directly proportional to the pressure of the gas.

Dalton, a contemporary of Henry, also concluded independently that the solubility of a gas in a liquid solution is a function of the partial pressure of the gas. If we use the mole fraction of the gas in the solution as a measure of its solubility, then:

The mole fraction of the gas in a solution is proportional to the partial pressure of the gas. For More Chemistry Formulascheck out the Main page of Physics Wallah.

Or, partial pressure of the gas in solution = KH mole fraction of the gas in solution Here KH is Henry’s law constant or, p = KHx

Different gases have different KH values at the same temperature. This suggests that KH is a function of the nature of the gas.

Henry’s law finds several applications in industry and explains some biological phenomena. Notable among these are:

1. To increase the solubility of CO2 in soft drinks and soda water, the bottle is sealed under high pressure.
2. To minimize the painful effects accompanying the decompression of deep sea divers, oxygen diluted with less soluble helium gas is used as breathing gas.
3. In the lungs, where oxygen is present in the air with high partial pressure, hemoglobin combines with oxygen to form oxyhemoglobin. In tissues where the partial pressure of oxygen is low, oxyhemoglobin releases oxygen for utilization in cellular activities.

Values Of Henry’s Law Constant (Kh) For Some Selected Gases In Water

Gas. Temp/K KH/kbar **He 293 144.97

H2 293 69.16

N2 293 76.48

N2 303 88.84

O2 293 34.86

O2 393 46.82**

It is obvious from the figure that the higher the value of KH at a given pressure, the lower the solubility of the gas in the liquid. It can be seen from the table that the KH value for both N2 and O2 increases with an increase in temperature indicating that the solubility of gases decreases with the increase in temperature. It is due to this reason that aquatic species are more comfortable in cold waters rather than warm waters.