Association Equation of State AEOS

Association equation of state (AEOS). To first introduce the concept of chemical compressibility factor and the association constant K, assume there are tiq moles of a substance in which ail the molecules are in the form of monomers, i.e., singly dispersed molecules. Then, if the fluid behaves as an ideal gas, PV = n HT, where Vq is the volume at pressure P. Let us now assume that some of the molecules will associate so that the true number of moles is then, the ideal gas PVTrela- 

If all the molecules form dimers, then = (l/2)rio and = 1/2. If all the molecules stay as monomers, Z - = 1. Next the association constant, K, is defined. 

Consider a mixture of monomers A and dimers A2 of a single-component system at temperature T and pressure P. Then 

Assume that the mixture of species A and A2 forms an ideal gas. The 

Similarly, enthalpy and entropy of trimer formation, etc. can be defined. For water, the experimentally determined A/i and As are available. 

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Solution of the association equation of state (AEOS). The incorporation of the association in the PR-EOS results in the following equation ... 

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