Ideal Gas Law Definition and Equation

Chemistry Glossary Definition of Ideal Gas Law

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The ideal gas law relates temperature, pressure, volume, and amount of a gas.

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The ideal gas law is also known as the general gas equation. It is an equation of state of an ideal gas that relates pressure, volume, quantity of gas, and temperature. While the law describes the behavior of a hypothetical gas, it approximates the behavior of real gases in many situations. The law was first stated by Émile Clapeyron in 1834. The law combines Boyle's law, Avogadro's law, Gay-Lussac's law, and Charles' law.


The ideal gas law is the relationship described by the equation"

PV = nRT

where P is pressure, V is volume, n is the number of moles of an ideal gas, R is the ideal gas constant, and T is the temperature.


  • Clapeyron, E. (1834). "Mémoire sur la puissance motrice de la chaleur." Journal de l'École Polytechnique (in French). XIV: 153–90.
  • Davis; Masten (2002). Principles of Environmental Engineering and Science. New York: McGraw-Hill. ISBN 0-07-235053-9.