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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.
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.
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 ...
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.
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
VTPR is a group contribution equation of state. [3] This is class of prediction methods combine equations of state (mostly cubic) with activity coefficient models based on group contributions like UNIFAC. [4] The activity coefficient model is used to adapt the equation of state parameters for mixtures by a so-called mixing rule. [5]
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.
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 ...