PHYSICAL CHEMISTRY IN BRIEF

CHAP. 6: THERMODYNAMICS OF HOMOGENEOUS MIXTURES [CONTENTS] 139

Chapter 6

Thermodynamics of homogeneous

mixtures

While Chapter 3 presented basic thermodynamic definitions and relations concerning pure
substances and mixtures with fixed composition, this chapter presents relations specific for
mixtures of variable composition.

6.1 Ideal mixtures

The simplest model used for the description of thermodynamic properties of mixtures is an
ideal mixturewhich is defined in the following section.

6.1.1 General ideal mixture.

The mixtures which obey Amagat’s law [see2.4.2] at all temperatures and pressures, i.e. the
mixtures for which we have

V =

∑k

i=1

niVm•,i, (6.1)

are called ideal mixtures.Vm•,iin this relation represent the volumes of pure components in the
same phase as the mixture at the temperature and pressure of the system, and the sum extends
over all components of the system.