Mass Action and Concentration Dependence of Chemical Potential

Abstract

The concept of mass action, its relation to the concentration dependence of the chemical potential (mass action equation), and subsequently, its relation to the chemical drive are discussed. An important application in the case of chemical equilibria is the derivation of the “mass action law.” But we also examine some further consequences such as the solubility of ionic solids and gases in liquids, preferably in water. The former leads us to the concept of solubility product, the latter to Henry’s law. With the help of Henry’s law, we can, for example, estimate the oxygen content in bodies of water, a parameter of prime importance for biological processes. Another relevant application results in Nernst’s distribution law which governs the distribution of a solute between two immiscible liquids. Distribution equilibria play a significant role in separating the substances in a mixture by the process of extraction or by partition chromatography. The last section of this chapter illustrates how the concept of mass action can be visualized with the help of potential diagrams.