v = zRT/P.

T`r = T/T`c.

P`r = P/P`c.

A technique of estimating physical properties of compound by using properties of molecular group of elements in the compound is called Group contribution method.

P`c = Pc(A)*y(A) + Pc(B)*y(B) + ………

Pseudocritical values for mixture of gases are calculated on the assumption that each component in the mixture contributes to the pseudocritical values in the same proportion as the mole fraction of that component in the gas is Kay’s Method.

T`c = Tc(A)*y(A) + Tc(B)*y(B) + ……..

Van der Waals, SRK and Peng Robinson are two, three and three parameter equation of state.

v = RT/P.

Pseudocritical values for mixture of gases are calculated on the assumption that each component in the mixture contributes to the pseudocitical values in the same proportion as the mole fraction of that component in the gas.