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**mixing enthalpy between those two components are:**

*ideal*(1) h

_{mix}= z

_{A}h

_{A}+ z

_{B}h

_{B}.

If I want to get the real behavior of a

**pure**component, I am also aware that; say for example, liquid enthalpy:

(2) h

_{L}= H

_{ref}+ ∫Cp

_{ig}dT (from T

_{ref}→ T) + h

_{RL}

I am assuming that if I want to calculate the, say,

**liquid enthalpy of a mixute A and B, the following holds true:**

*non-ideal*(3) h

_{Lmix}= x

_{A}h

_{L,A}+ x

_{L,B}h

_{B}+ h

_{RLmix}

where h

_{RLmix}is defined as the liquid departure enthalpy as predicted by any equation of state; and that h

_{L,A}and h

_{L,B}is basically (2) in this post; ie. the final equation that I am looking for is:

(4) h

_{Lmix}= x

_{A}[H

_{ref,A}+ ∫Cp

_{ig,A}dT (T

_{ref}→ T) + h

_{RL,A}] + x

_{L,B}[(H

_{ref,B}+ ∫Cp

_{ig,B}dT (T

_{ref}→ T) + h

_{RL,B}] + h

_{RLmix}

What I'm after is, if I am going for modelling non-ideal mixtures, I have to calculate the departure enthalpies of each component (to be added to the pure component enthalpies), then the departure enthalpy of the mixture itself (to be added to the final mixture equation ie. (3))? I am theorizing that the enthalpy departure of the mixture is independent of the enthalpy departure of a pure component at a certain T and P. Also, this holds true for vapors, yes?

I'd like a straightforward answer, I am getting really confused from all these quantities.