The chemical potential is equal to the partial derivative of this quantity with respect to the number of particles.
The change in this quantity for mixing is equal to the sum of the products of the component's mole fraction and the natural log of the mole fraction times RT.  When temperature is constant, the partial derivative of this quantity with respect to pressure is volume. The chemical potential is equal to the partial derivative of this quantity with respect to the number of particles. The equilibrium constant is equal to the exponential of negative RT dividing the change in this quantity. It is equal to enthalpy minus the product of temperature and entropy.  For 10 points, name this quantity that when the change in it is negative indicates a reaction is spontaneous, and which is symbolized G.
The change in this quantity for mixing is equal to the sum of the products of the component's mole fraction and the natural log of the mole fraction times RT.  
Gibbs Free Energy