A Multiphase, Multireaction System

Consider a closed system, containing A species involved in r independent reactions and distributed among l phases, which is in equilibrium at some temperjiture T and pressure P. 

The total number of intensive variables is again k -1) + 2, but the number of equations becomes k i - 1) + r, i.e. it is increased by the number of reactions r, since for each reaction Eq. 12.6.10 must be satisfied. The degrees of freedom are, therefore  

Identification of the independent reactions that lead to an equilibrium mixture is not always apparent, and it will be discussed in Chapter 15. In the presence of special constraints, Eq. 12.7.3 becomes  

Finally, Duhem s theorem - as it will be demonstrated in Chapter 15 -applies to reacting systems as well. 

At this point, undergraduate students can move on to Section 12.10. 

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