For an ideal gas this quantity is equal to the fundamental temperature tau times the natural logarithm of the ratio of particle concentration to quantum concentration. The dif
For an ideal gas this quantity is equal to the fundamental temperature tau times the natural logarithm of the ratio of particle concentration to quantum concentration. The difference in this quantity from a reference state equals RT times the natural logarithm of the ratio of fugacity to the reference fugacity. Changes  in this quantity for each species in a system are related to changes in temperature and pressure via the (*) Gibbs-Duhem equation. When other variables are constant, this quantity equals the partial derivative of Gibbs free energy with respect to particle number, so it is the conjugate variable of particle number. For 10 points, name this quantity representing the change in energy when a particle is added to a solution, and which is symbolized mu. 
For an ideal gas this quantity is equal to the fundamental temperature tau times the natural logarithm of the ratio of particle concentration to quantum concentration.
chemical potential [prompt on "mu" until it is read]