Gas Density Calculator

Table of content
1. Gas Density Formula
2. Gas Density Calculation
3. Gas Density Calculator

Gas Density Formula

Density of an ideal gases is a function of pressure, molecular weight of the pure gas or mixture and the temperature of the gas.

Ideal gas equation is,
PV = nRT
where, P = Pressure (bar, atmosphere, Pa)
V = Gaseous volume (m3, cm3)
n = number of gaseous moles (dimensionless)
R = Universal gas constant (J/mol.K, lit.atm/mol.K)
T = Temperature of the gas (K)

M = molecular weight of the gaseous phase
W = n X M =  mass of the gaseous phase

To get the gas density formula,
PV = (W/M) RT
PM / RT = W/V
W/V = ρ = mass per unit volume, i.e. density
ρ = PM / RT  .................. formula for ideal gas density

For a real gas with compressibility factor z,
ρ = PM / zRT ..... formula for real gas density calculation

Gas Density Calculation

Understand how to calculate gas density by using an example problem.


Calculate the density of air at a temperature of 25°C (298.15 K) and a pressure of 1 atm (101.325 kPa).


Formula for calculating gas density derived from the ideal gas law is:
ρ = PM / zRT
where: ρ = density, M = molar mass, P = pressure,
R = universal gas constant, T = temperature

Molar mass of Air M = 28.96 grams/mole
P = 1 atm
T = 298.15 K
R = 0.0821 L·atm/mol·K
Air is considered to be a nearly ideal gas, so the compressibility of air is set at Z=1 .

Substituting the given values, we have:
ρ = PM / zRT
= (1 atm) (1) (28.96 g/mol) / (0.0821 L·atm/mol·K)(298.15 K) = 1.183 g/L = 1.183 kg/m3

Therefore, the density of air at 25°C and 1 atm is approximately 1.183 kg/m3.

Gas Density Calculator

Check EnggCyclopedia's Gas Density Calculator for quick calculation of gas density..

This is a sample of the Gas Density calculator. To access the working calculator, please sign up for free membership trial. Use this it for quick gas density calculation based on the molecular weight, temperature, pressure and z factor for the gas.


Molecular Weight
Compressibility (z)
Calculated gas density = kg/m3

Also refer to EnggCyclopedia's Liquid Density Calculator.


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