Liquid-Liquid Miscibility for Organic Acids with Methanol
Liquid miscibility is the measure of how well a pair of liquids mixes/dissolves. The miscibility of two liquids depends on the Gibbs free energy of the system, which is a function of temperature, enthalpy and entropy . The difference in free energy between the mixture and its pure components is given by . In the two-component systems modeled in this Demonstration, increasing or decreasing the mole fraction of one component such that the total number of moles always adds up to 1 changes the enthalpy and entropy of the system. This in turn changes the free energy of the system. This Demonstration assumes constant temperature, and shows two examples: methanol/propionic acid and methanol/acetic acid. When the mole fraction of methanol, which can be manipulated with the slider, gives the lowest , the system is thermodynamically in the most stable state.
Snapshot 1: the most favorable state of propionic acid and methanol as Gibbs free energy is minimized
Snapshot 2: the mole fraction of methanol is equal to .1; this can be described as a solution of methanol in propionic acid
Snapshot 3: the mole fraction of methanol is equal to .9, and is therefore a solution of propionic acid in methanol
 R. Haase and R. Lorenz, "Enthalpies of Mixing for Binary Liquid Mixtures of Monocarbonic Acids and Alcohols," Zeitschrift für Naturforschung A, 40(9), 1985 pp. 947–951.
Submission from the Compute-to-Learn course at the University of Michigan.