Evaluation of the Equilibrium Conversion

As we have seen in Section 12.5.3, the number of moles of component i of the reaction mixture at equilibrium is given by  

the total number of moles present at equilibrium is  

All mole fractions are, therefore, expressed in terms of a single variable, e, which can be evaluated from the known value of K. The equilibrium conversions are then calculated from Eq. 15.4.3. 

At low pressures can be set equal to 1, and the fact that most gas-phase reactions take place at relatively high temperatures for kinetic purposes, provides additional support for this assumption. 

At higher pressures can be substantially different from unity even at high temperatures, as we will see with the case of the ammonia synthesis (Example 15.7). In such cases can be estimated with an equation of state. This requires an iterative calculation which is initialized by setting k = 

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Example 12.7 demonstrates that knowledge of K leads to the evaluation of the equilibrium conversion. 

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