# Ideal Gas Law

The ideal gas law defines the properties of a gas assuming it behaves ideally. For most cases, gases behave close enough to ideal that the ideal gas law can be employed to predict its behaviour with little error. The ideal gas law defines the relationship between a gas' pressure $P$ (Pa), the volume it occupies $V$ (m$^3$)and its temperature $T$ (K):

$PV = nRT$

where $n$ (mol) is the number of moles of gases there is (measure of amount of atoms or molecules), and $R$ (J/K$^{-1}$mol$^{-1}$) is the ideal gas constant.

It is often convenient to rewrite the ideal gas law using unit of grams to measure the mass of the gas:

$PV = m\frac{R}{M}T$

or
$P=\rho R_{specific}T$

where $M$ (kg/mol) is the molar mass of the gas, $m$ (kg) is the mass of the gas, $\rho$ (kg/m$^3$) is the gas' density, and $R_{specific} = \frac{R}{M}$ (J/kg$^{-1}$K$^{-1}$) is the specific gas constant of the gas. Every gas has a different molar mass; for example, Air, made up of a number of gases, has a molecular mass of 28.97 g/mol.

#### Videos on Ideal Gases

Crash Course: Chemistry #12 - Ideal Gas Laws

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