Redlich–Kwong equation of state

The Redlich - Kwong equation of state is an equation of state for real gases. It reads:

The individual symbols stand for the following sizes:

• Vm - molar volume
• T - temperature
• Tc - critical temperature
• P - pressure
• R - universal gas constant
• A - Cohesion pressure
• B - covolume

This equation 1949 is found only a marginal improvement of the van der Waals equation dar. by their comparatively simple form is however still of interest. A poor approximation shows for liquid phases, so the equation can not be used for gas - liquid equilibria. This disadvantage can, however, be compensated by the separate use of better adapted equations.

The Redlich - Kwong equation is suitable for the calculation in gas phase, when the ratio of pressure to critical pressure is less than half the ratio of temperature to critical temperature. Synonymous this: the reduced pressure may only have at most half the size of the reduced temperature Tr:

A further development of Soave - Redlich constitutes - Kwong equation of state and the equation of state PSRK