Real Gases

Standard or Perfect Gas Equation
Gases which obey all gas laws in all conditions of pressure and temperature are called perfect gases.
Equation of perfect gas pV=nRT
where p = pressure, V = volume, T = absolute temperature, R = universal gas constant and n =
number of moles of a gas.
Universal gas constant R = 8.31 J mol K .
Real Gases
Real gases deviate slightly from ideal gas laws because
Real gas molecules attract one another.
Real gas molecules occupy a finite volume.
Real or Van der Waal’s Gas Equation
(p + a/V ) (V – b) = RT
where a and b are called van der Waals’ constants.
Pressure due to an ideal gas is given by
p = (1/3).(mn/V). c = 1/3 ρ c
For one mole of an ideal gas
P = (1/3).(M/V).c
where, m = mass of one molecule, n = number of molecules, V = volume of gas, c = (c + c + … +
c ) / n allde root mean square (rrns) velocity of the gas molecules and M = molecular weight of the
gas. If p is the pressure of the gas and E is the kinetic energy per unit volume is E, then
p = (2/3).E