Concise Physical Chemistry

c07 JWBS043-Rogers September 13, 2010 11:25 Printer Name: Yet to Come

7 Equilibrium

Chemists are often depicted in the popular media as sinister fellows who pour a

solution from beaker A into beaker B with catastrophic results. In fact, we are neither

more nor less sinister than the next person and we take elaborate precautions to avoid

catastrophies. Nevertheless, the process of adding one or many components A of one

kind to a system of another kind B to establish an equilibrium mixtureiscentral to

our art or science, and the theoretical examination of chemical equilibrium is the high

point and culmination of classical chemical thermodynamics.

7.1 THE EQUILIBRIUM CONSTANT

Suppose that gases A and B are capable of equilibration

A(g) →← B(g)

and arbitrary amounts of A(g) and B(g) are introduced into a closed container at 298 K.

Because the amounts are arbitrary, the quotient of the partial pressuresQ=pB/pA

in the container will not be the equilibrium constantKeq. The chemical potentialsGA

andGBwill probably not be in the standard state. Instead they will differ fromG◦A

andG◦B,by

GA=G◦A+RTln

pA

1. 0

Concise Physical Chemistry,by Donald W. Rogers

Copyright©C2011 John Wiley & Sons, Inc.

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