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.
Also refer to EnggCyclopedia's Liquid Density Calculator.