Using the definition of the Gibbs free energy it is possible to state the general inequality for Equilibrium and irreversibility, ΔS^* ≥0, for processes at constant P and T in a way that involves system variables only, i.e., ΔG ≤0. Find a corresponding criterion for processes at constant V and T. The new thermodynamic variable that is used to express this criterion is called the Helmholtz free energy?