Solutions, Phase-Separated Systems, Colligative Properties and Phase Diagrams

Abstract

This chapter covers a wide range of related topics: chemical potential of substances in solutions, ideal solutions obeying Raoult’s law, ideal dilute solution for which the solute follows Henry’s law, and the underlying molecular behaviour expressed in the simplest manner, by the so-called mean field approximation and how the Gibbs free energy as a function of solution composition can be used to construct phase diagrams. An important mission is to be able to read a phase diagram properly; this is explained by several examples. Spinodal decomposition, nucleation-controlled phase separation and the lever rule are explained in detail. Colligative properties, e.g. osmotic pressure, are thoroughly dealt with, and relationships between the colligative properties and the solute concentration are derived.