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Mixtures

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Partial Molar Volume

The partial molar volume is broadly understood as the contribution that a component of a mixture makes to the overall volume of the solution.

Liquid-liquid phase diagrams

These diagrams are temperature composition diagrams for systems of two partially miscible liquids (that is, liquids which do not mix in all proportions at all temperatures). The interpretation of these diagrams is in principle precisely the same as that of liquid-vapour diagrams.

Temperature Composition Diagrams

These are phase diagrams which show the composition of two phases in equilibrium at a given pressure, and how these compositions change with temperature (as opposed to the pressure composition diagrams which showed the pressure dependence of the composition at a fixed temperature).

Pressure Composition Diagrams

These diagrams combine information about the composition of the liquid and vapour phases at a given temperature, and how the compositions of the phases change with pressure.

The Gibbs-Duhem Equation

We have stated on the previous page that the total Gibbs energy of a binary mixture is given by.

Vapour Pressure Diagrams

These diagrams consider two component systems at a constant temperature. The two remaining variables that affect the stabilities of the phases are the pressure and the composition of the mixture, so a vapour phase diagram represents diagrammatically the compositions and pressures at which the condensed and vapour phases of the mixture are stable.

Partial Molar Gibbs Energy

We have already remarked that, for a pure substance, the chemical potential is just another name for the molar Gibbs energy.