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The Redlich–Kwong equation is very similar to the Van der Waals equation, with only a slight modification being made to the attractive term, giving that term a temperature dependence. At high pressures, the volume of all gases approaches some finite volume, largely independent of temperature, that is related to the size of the gas molecules.
In 1972 G. Soave [4] replaced the term of the Redlich–Kwong equation with a function α(T,ω) involving the temperature and the acentric factor (the resulting equation is also known as the Soave–Redlich–Kwong equation of state; SRK EOS).
Critical isotherm for Redlich-Kwong model in comparison to van-der-Waals model and ideal gas (with V 0 =RT c /p c) The Redlich–Kwong equation is another two-parameter equation that is used to model real gases. It is almost always more accurate than the van der Waals equation, and often more accurate than some equations with more than two ...
The Soave–Redlich–Kwong equation of state describes the vapor densities of pure components and mixtures quite well, but the deviations of the liquid-density prediction are high. For the VLE prediction of mixtures with components that have very differing sizes (e. g. ethanol, C 2 H 6 O, and eicosane, C 20 H 42) larger systematic errors are ...
Hence, all cubic equations of state can be considered 'modified van der Waals equation of state'. There is a very large number of such cubic equations of state. For process engineering, cubic equations of state are today still highly relevant, e.g. the Peng Robinson equation of state or the Soave Redlich Kwong equation of state.
The most famous functional forms of this category are Redlich-Kwong, [3] Soave-Redlich-Kwong [4] and Peng-Robinson. [5] Although their initial form is empirically suggested, they are categorised as semi-empirical models as their parameters can be adjusted to fit the real experimental measurement data of the target system.
Almost all subsequent equations of state are derived from the van der Waals equation, like those from Dieterici, [7] Berthelot, [8] Redlich-Kwong, [9] and Peng-Robinson [10] suffer from the singularity introduced by 1/(v - b). Other equations of state, started by Beattie and Bridgeman, [11] are more closely related to virial equations, and show ...
Kwong returned to 3M in 1951 as a senior chemical engineer in the Chemical Division, working there until retirement in 1980, at the age of 64. The development of the Redlich-Kwong equation was the last significant theoretical treatment of thermodynamics. He died of pneumonia in Saint Paul, Minnesota, on January 4, 1998, at the age of 81.