ABSTRACT
In Chapter 14, we considered pure liquids or solids composed of a single chemical species. Here we consider solutions, i.e., homogeneous mixtures of more than one component. The fundamental result that we derive in this chapter, μ = μ ∘ + kT ln x, is a relationship between a molecule’s chemical potential μ and its concentration x in the solution. This relationship will help address questions in Chapters 16 and 25–31: When does one chemical species dissolve in another? When is it insoluble? How do solutes lower the freezing point of a liquid, elevate the boiling temperature, and cause osmotic pressure? What forces drive molecules to partition differently into different phases? We continue with the lattice model because it gives simple insights and because it gives the foundation for treatments of polymers, colloids, and biomolecules.
