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# Redlich-Kwong equation of state

The **Redlich-Kwong equation of state** is ^{[1]}:

- .

The Redlich-Kwong equation of state has a critical point compressibility factor of ^{[2]}:

leading to

and

where is the pressure, is the temperature and is the molar gas constant. is the critical temperature and is the pressure at the critical point.

## Soave Modification[edit]

A modification of the the Redlich-Kwong equation of state was presented by Giorgio Soave in order to allow better representation of non-spherical molecules^{[3]}. In order to do this, the square root temperature dependence was replaced with a temperature dependent acentric factor ():

where is the critical temperature. This leads to an equation of state of the form:

or equivalently:

## References[edit]

- ↑ Otto Redlich and J. N. S. Kwong "On the Thermodynamics of Solutions. V. An Equation of State. Fugacities of Gaseous Solutions", Chemical Reviews
**44**pp. 233-244 (1949) - ↑ Reino. W. Hakala "The value of the critical compressibility factor for the Redlich-Kwong equation of state of gases", Journal of Chemical Education
**62**pp. 110-111 (1985) - ↑ Giorgio Soave "Equilibrium constants from a modified Redlich-Kwong equation of state", Chemical Engineering Science
**27**pp. 1197-1203 (1972)