Which law states that the solubility of a gas in a liquid varies in proportion to the partial pressure of that gas in the overlying space?

Henry's Law is the principle that describes how the solubility of a gas in a liquid is directly proportional to the partial pressure of that gas over the liquid. This relationship implies that if the pressure of the gas increases, more gas will dissolve in the liquid until a new equilibrium is achieved. This law is critical in various scientific and practical applications, particularly in areas like scuba diving, ecotoxicology, and environmental chemistry, where the behavior of gases dissolved in liquids is essential to understand.

The mathematical expression of Henry's Law involves a constant (Henry's Law constant) that is unique to each gas-liquid combination, allowing predictions about solubility under specific pressure conditions. Additionally, this principle helps clarify concepts related to gas exchange in biological systems, such as in the lungs of divers, where the pressure of inhaled gases can significantly impact their solubility in blood.

Other laws mentioned, like Dalton's Law, relate more to the behaviors of gases in a mixture rather than their solubility, while Guy-Lussac's Law pertains to the relationship between the temperature and pressure of a gas and does not address solubility in liquids. The Henderson-Hasselbalch equation also does not apply here, as it is used for calculating p