Partial pressure

The pressure a component gas in a mixture would exert if it alone occupied the mixture’s volume at the same temperature. In an ideal gas mixture, each component’s partial pressure is proportional to its mole fraction.

Dalton’s law of partial pressures: For an ideal gas mixture, total pressure equals the sum of the component gases’ partial pressures. It states how component pressures combine to give the mixture’s total pressure.
Henry’s law: A relation between a gas’s partial pressure above a liquid and its dissolved concentration at equilibrium. It uses partial pressure to predict how much gas dissolves in a liquid.
Pressure: Force exerted per unit area by particles or other physical interactions. Partial pressure is a component-specific contribution to the pressure of a gas mixture.
Fugacity: A thermodynamic quantity representing a real substance’s effective pressure in chemical-equilibrium calculations. It replaces pressure in many real-gas calculations when ideal-mixture behavior fails.
Ideal gas law: An equation relating a gas’s pressure, volume, temperature, and amount: PV = nRT. Applied to a mixture component, it gives that gas’s partial pressure.
Alveolar gas equation: An equation estimating oxygen partial pressure in the lung alveoli from inspired gas and carbon dioxide levels. It applies partial-pressure accounting to oxygen available for exchange in the lungs.
Temperature: A physical quantity that characterizes thermal state and determines the direction of heat transfer. The definition compares a component gas at the mixture’s temperature.
Vapor pressure: The pressure of a vapor in equilibrium with its condensed phase at a specified temperature. It is a phase-equilibrium pressure, unlike a component’s share of a gas mixture’s pressure.
Mole fraction: The fraction of a mixture’s total amount contributed by one component. In an ideal gas mixture, multiplying mole fraction by total pressure gives partial pressure.
Oxygen therapy: Medical treatment that increases the oxygen concentration in inspired gas to improve oxygen availability. Raising inspired oxygen increases its partial pressure and can raise blood oxygenation.

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