Density of Gases

Author:Matthias Boularot

Created on:12 Mar 2025

Last updated on:12 Mar 2025

The density of gasses is defined by :

ρ = \frac{P \cdot M}{Z \cdot R_{U} \cdot T}

With

$ρ$

Density [

kg \cdot m^{-3}

]

$P$

Absolute Pressure [

Pa

]

$M$

Molar Mass [

g \cdot {mol}^{-1}

]

$Z = (T, P, ...)$

Gas Compressibility Factor [

\emptyset

]

The gas compressibility factor is a dimensionless quantity which describes how much a real gas deviates from ideal gas behavior when subjected to changes in pressure and temperature. In other words, it quantifies the extent to which a gas's volume changes in response to changes in pressure and temperature. For an ideal gas, the compressibility factor is always equal to 1 at any pressure and temperature.

When Z is greater than 1, the gas is more compressible than an ideal gas, and its volume decreases more than expected with increasing pressure. When Z is less than 1, the gas is less compressible than an ideal gas, and its volume increases more than expected with decreasing pressure.

The density of real gases depends on a combination of factors, including pressure, temperature, molecular properties, molecular interactions, and the compressibility factor. These factors interact to determine the behavior of real gases and their density under different conditions. In practice, the density of a real gas is calculated using experimentally measured data. For example, REFPROP is a database/software developed by NIST that accurately calculates thermodynamic and transport properties of fluids, including actual density.