Ideal Gas Mixtures and Liquid Solutions
 
We next explore the development of a quantitative definition of the chemical potential in terms of the volumetric properties and composition of mixtures. We have observed earlier that just as ideal gas state is a reference for real gas properties, ideal gas mixtures play the same role with respect to real gas mixtures. Therefore, it is instructive to establish the property relations for ideal gas mixture first.
Consider the constitution of an ideal gas mixture (containing N species) at a given temperature (T) and pressure (P). To obtain n moles of the total mixture we need to bring together n_{i} moles of each species at temperature T but at a pressure p_{i} which corresponds to the partial pressure that each species would exert in the final mixture. If V^{t} is the total volume of the mixture, the following set of relations hold.
 
