PlanetPhysics/Ideal Gas Law

The equation that characterizes any amount of a gas is $$ pV = nRT $$ where $$p$$ is the pressure, $$V$$ the volume, $$n$$ the number of the gas moles and $$T$$ the absolute temperature of the gas; $$R$$ the universal gas constant (approximately 8.314472 $$\frac{\mbox{Pa}\cdot\mbox{m}^3}{\mbox{mol}\cdot\mbox{K}}$$).

The gas law is accurately valid for an ideal gas, but a good approximation for real gases.

The law contains the following gas laws:


 * Boyle--Mariotte law ($$pV =$$\, constant when $$n$$ and $$T$$ are constants)
 * Gay--Lussac law ($$\frac{V}{T} =$$\, constant when $$n$$ and $$p$$ are constants)
 * Avogadro's law (in equal conditions, equal volumes of different gases contain the same number of molecules)

Alternative definition
The ideal gas law can also be defined using Boltzmann's constant: $$ pV = NkT $$ The symbols are those defined above, with the difference that $$N$$ is the number of gas molecules, and $$k$$ is the Boltzmann constant, $$k \approx 1.38 \times 10^{-23} \mbox{JK}^{-1}$$. This form is often preferred by physicists who consider the number of molecules to be more fundamental than the number of moles.