Compressibility Factors Using the Soave-Redlich-Kwong Equation of State
The Soave–Redlich–Kwong equation of state can accurately describe a compound in both liquid and vapor phases. This Demonstration applies this equation of state to estimate and plot the compressibility factor, , versus reduced pressure, , for ethane at various values of the reduced temperature, .
In the Soave–Redlich–Kwong equation of state, the compressibility factor is a solution of the following cubic equation:
where and with , , , and . Here is the acentric factor, and are the critical temperature and pressure, and = is the reduced temperature.
For ethane, , , and .
For more information on the compressibility factor, see http://en.citizendium.org/wiki/Compressibility_factor.
 Z. Nasri and H. Binous, "Applications of the Soave-Redlich-Kwong Equation of State Using Mathematica," Journal of Chemical Engineering of Japan, 40(6), 2007 pp. 534–538.