What is "molar volume"

n. (context chemistry physics English) The volume occupied by one mole of a substance (especially of a gas)

The molar volume, symbol V, is the volume occupied by one mole of a substance ( chemical element or chemical compound) at a given temperature and pressure. It is equal to the molar mass (M) divided by the mass density (ρ). It has the SI unit cubic metres per mole (m/mol), although it is more practical to use the units cubic decimetres per mole (dm/mol) for gases and cubic centimetres per mole (cm/mol) for liquids and solids.

The molar volume of a substance can be found by measuring its molar mass and density then applying the relation

$V_{\rm m} = {M\over\rho}$.

If the sample is a mixture containing N components, the molar volume is calculated using:

$V_{\rm m} = \frac{\displaystyle\sum_{i=1}^{N}x_{i}M_{i}}{\rho_{\mathrm{mixture}}}$.

For ideal gases, the molar volume is given by the ideal gas equation: this is a good approximation for many common gases at standard temperature and pressure. For crystalline solids, the molar volume can be measured by X-ray crystallography.