The effect of gas imperfection on chemical equilibrium

The equations derived in the preceding paragraph can be used to calculate the effect of pressure upon the affinity and equihbrium constant in a mixture of reacting gases. 

We begin by calculating the Gibbs free energy of an imperfect gas mixture. Employing the van der Waals equation and inserting the virial coefficient (11.35) into (11.21), remembering that B =B/RT, we have 

The affinity of the reaction is obtained simply by differentiating with respect to (c/. 4.30)  

Following the method employed in 1 of this chapter we introduce an equilibrium parameter K defined by (11.11), whence 

This equation gives the effect of gas imperfection on the equilibrium constant we notice that as p - 0, K reduces to 

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