Henry's Law

Henry's Law is a fundamental principle in physical chemistry that describes the relationship between the solubility of a gas in a liquid and the partial pressure of the gas above the liquid. Formulated by the British chemist William Henry in 1803, Henry's Law is an essential concept in fields such as chemical engineering, environmental science, and medicine, particularly in understanding how gases dissolve in blood and other fluids.

Statement of Henry's Law

Henry's Law can be stated as: "At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid." Mathematically, it is expressed as:

\[ C = kP \]

where:

• \(C\) is the concentration of the dissolved gas in the liquid,
• \(k\) is Henry's law constant, and
• \(P\) is the partial pressure of the gas.

Henry's law constants are specific to each gas-liquid combination and vary with temperature and the nature of the solvent.

Applications of Henry's Law

Henry's Law has wide-ranging applications across various disciplines:

• In environmental science, it helps in understanding the behavior of pollutants between water bodies and the atmosphere.
• In chemical engineering, it is crucial for designing processes involving gas-liquid mixtures, such as gas scrubbing and distillation.
• In the beverage industry, it explains the dissolution of carbon dioxide in soft drinks and beers under pressure.
• In medicine, it is used to calculate the solubility of gases in blood, which is critical for anesthesia and understanding decompression sickness.

Limitations

While Henry's Law provides a good approximation under many conditions, it has limitations. It is most accurate for dilute solutions and low gas pressures. At high pressures or with gases that react chemically with the solvent, deviations from Henry's Law occur.

See Also

• Dalton's Law of Partial Pressures
• Raoult's Law
• Solubility
• Gas Laws