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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.
PSRK is a group-contribution equation of state. This is a class of prediction methods that combines equations of state (mostly cubic) with activity coefficient models based on group contributions, such as UNIFAC. The activity coefficient model is used to adapt the equation-of-state parameters for mixtures by a so-called mixing rule.
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 ...
Otto Redlich (November 4, 1896 – August 14, 1978) was an Austrian physical chemist who is best known for his development of equations of state like the Redlich-Kwong equation. [ 1 ] [ 2 ] Redlich also made numerous other contributions to science.
The van der Waals equation of state may be written as (+) =where is the absolute temperature, is the pressure, is the molar volume and is the universal gas constant.Note that = /, where is the volume, and = /, where is the number of moles, is the number of particles, and is the Avogadro constant.
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.
His new formula revolutionized the study of equations of state, and was the starting point of cubic equations of state, which most famously continued via the Redlich–Kwong equation of state [7] and the Soave modification of Redlich-Kwong. [8] The van der Waals equation of state can be written as
I'm expanding this article for a class. I was going to give a little bit more background to the equation itself, citing Redlich and Kwong's 1949 paper. I'll go into a little bit of their derivation of it. I'm then going to talk about some of the modifications that have been made to the equation over the years.