We know that the Gibbs energy of an equilibrium state must be minimum with respect to all possible changes at the given T and P.

a) Use the first and second laws of thermodynamics to derive an expression that gives the general criterion for stability.

b) Show the function for assessing the stability of a system, whose volume and temperature are kept constant.

c) Draw schematically the molar Gibbs energy of a single component system kept at a constant pressure as a function of temperature. Explain why the curve should look like the way you draw it based on equations.

d) If we mix two liquids at constant T and P, the total Gibbs energy must decrease or increase? Explain using equations.