There are many cases here the effective concentration of a solute differs from the value we would expect based on the mass of compouind that isin solution. This is an example of non-ideal behavior. We cll the effective of non-ideal concentration, the activity. In this section we discuss how to think of activity and we review the application of chemical potential to the derivation of Delta G, the free energy of reaction. It is important that we understand that whether we use activity or the ideal concentration the standard state remains the same. It is always 1 bar of pressure or 1 molar of concentration in solution. This is discussed in the following segment.
