Partial Molar Enthalpy
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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 
-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.
Contributed by: Simon M. Lane and Rachael L. Baumann (April 2014)
With additional contributions by: John L. Falconer and Nick Bongiardina
(University of Colorado Boulder, Department of Chemical and Biological Engineering)
Open content licensed under CC BY-NC-SA
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 
:
Where 
is the partial molar enthalpy of component 
and 
is the partial molar enthalpy of component 
. A screencast video at [1] shows how to use this Demonstration, and a screencast at [2] presents an example.
References
[1] Partial Molar Enthalpy. http://www.learncheme.com/simulations/thermodynamics/thermo-2/partial-molar-h
[2] Partial Molar Properties: Binary Solutions [Video]. (Apr 5, 2012) www.youtube.com/watch?v=TFmIPEG_X3A.
Snapshots
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