Volume occupied by one mole of a substance (chemical element or chemical compound) at a given pressure $\begin{array}{l}p\end{array}$ and temperature $\begin{array}{l}T\end{array}$ :

(1)	$\begin{array}{l}\displaystyle V_m(p, T) = \frac{V}{\nu} =\frac{M}{\rho}= \frac{1}{\rho_m} = \frac{N_A}{n}\end{array}$

where

$\begin{array}{l}V\end{array}$	volume	$\begin{array}{l}M\end{array}$	molar mass of a substance	$\begin{array}{l}n\end{array}$	Molecular Concentration
$\begin{array}{l}\nu\end{array}$	amount of substance	$\begin{array}{l}\rho\end{array}$	density of a substance	$\begin{array}{l}N_A\end{array}$	Avogadro constant (6.022140758(62) · 10²³ mol⁻¹ )

SI Unit	Oil Metric Unit	Oil Field Unit
m³/ mol	m³/ mol	m³/ mol

Molar volume $\begin{array}{l}V_m\end{array}$ is directly related to the average intermolecular distance $\begin{array}{l}V_m\end{array}$ and in case of isotropic substance: $\begin{array}{l}V_m = N_A \cdot d^3\end{array}$ .

Molar volume $\begin{array}{l}V_m\end{array}$ is inverse to Molar Density $\begin{array}{l}\rho_m\end{array}$ :

(2)	$\begin{array}{l}\displaystyle V_m = \frac{1}{\rho_m}\end{array}$

In case of fluid which satisfies Real Gas EOS @model the Molar volume $\begin{array}{l}V_m\end{array}$ can be expressed in terms of Z-factor $\begin{array}{l}Z(p, T)\end{array}$ :

(3)	$\begin{array}{l}\displaystyle V_m = \frac{ZRT}{p}\end{array}$

where

$\begin{array}{l}T\end{array}$	temperature
$\begin{array}{l}p\end{array}$	pressure
$\begin{array}{l}R\end{array}$	gas constant

Molar volume of the mixture is:

(4)	$\begin{array}{l}\displaystyle V_m(p, T) =\frac{M}{\rho_f} = \frac{\sum_k M_k \cdot x_k}{\rho_f}\end{array}$

where

$\begin{array}{l}M_k\end{array}$	molar mass of the k-th mixture component
$\begin{array}{l}x_k\end{array}$	mole fraction of the k-th mixture component
$\begin{array}{l}\rho_f\end{array}$	mixture density

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See also

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Molar volume = Vm

See also