CHAPTER 12
12 Equilibrium Conditions in Multicomponent Systems
MULTICOMPONENT SYSTEMS
This chapter applies equilibrium theory to a variety of chemical systems of more than one
component. Two different approaches will be used as appropriate: one based on the relation
íi Dìi for transfer equilibrium, the other based on
P
iii D^0 orK D
Q
ia
i
i for
reaction equilibrium.
12.1 Effects of Temperature
For some of the derivations in this chapter, we will need an expression for the rate at which
the ratioi=Tvaries with temperature in a phase of fixed composition maintained at con-
stant pressure. This expression leads, among other things, to an important relation between
the temperature dependence of an equilibrium constant and the standard molar reaction
enthalpy.
12.1.1 Variation ofi=T with temperature
In a phase containing speciesi, either pure or in a mixture, the partial derivative ofi=T
with respect toTat constantpand a fixed amount of each species is given by^1
@ .i=T /
@T
p;fnig
D
1
T
@i
@T
p;fnig