Van der Waals equation

An equation of state that models real gases by correcting the ideal-gas law for finite molecular size and intermolecular attraction.

Ideal gas law: An equation of state relating pressure, volume, temperature, and amount for a gas whose particles have negligible volume and interactions. It is the limiting model recovered when the Van der Waals corrections vanish.
Equation of state: A relation connecting thermodynamic state variables such as pressure, volume, and temperature. The Van der Waals equation is one specific relation among these state variables.
Johannes Diderik van der Waals: Dutch physicist who developed an equation of state for real gases and received the 1910 Nobel Prize in Physics. His 1873 doctoral thesis introduced the equation and its molecular corrections.
Van der Waals constants: Substance-specific parameters a and b that represent intermolecular attraction and excluded volume in the Van der Waals equation. Their values determine the equation's predictions for a particular gas.
Redlich–Kwong equation of state: A cubic equation of state that modifies the attraction term to improve predictions for gases and liquids. It offers better quantitative performance than the original Van der Waals form.
Excluded volume: The volume made inaccessible to particle centers because particles occupy finite space. The parameter b reduces the volume available for molecular motion.
Molar volume: The volume occupied by one mole of a substance. The molar form uses molar volume to express the equation for one mole of gas.
Ideal gas: A theoretical gas whose particles have negligible volume and exert no intermolecular forces. Van der Waals modified this idealization to account for real molecular behavior.
Fluid phase diagram: A map of a substance's stable phases as functions of variables such as temperature and pressure. The equation generates characteristic liquid–gas coexistence and critical behavior.
Soave–Redlich–Kwong equation of state: A cubic equation of state with a temperature-dependent attraction parameter adjusted using vapor-pressure data. Its temperature correction improves vapor–liquid equilibrium predictions.

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