Partial Molar Enthalpy

The molar enthalpy of a binary mixture (blue curve) of and is plotted as a function of the mole fraction of component . The end points of the molar enthalpy are the pure-component enthalpies and . The partial molar enthalpies and are obtained by drawing a tangent line (black, dashed) at the black point, which indicates the mole fraction of the solution. The intersections of this tangent with the y-axis at and correspond to and , respectively. You can change the mole fraction of in the mixture and the non-ideal parameter, which represents deviation from an ideal solution, with sliders. For an ideal solution the non-ideal parameter is zero, and the enthalpy of the mixture is a linear function of the molar enthalpies of the pure components.

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DETAILS

The molar enthalpy is:
,
where is the enthalpy (kJ/mol), and are the compositions of and , and is a non-ideal parameter.
The partial molar enthalpy is represented by a line tangent to at composition of the mixture :
.
A screencast video at [1] shows how to use this Demonstration, and a screencast at [2] presents an example.
References
[2] Partial Molar Properties: Binary Solutions [Video]. (Apr 5, 2012) www.youtube.com/watch?v=TFmIPEG_X3A.
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