Enthalpy as a state function

[MedPR]

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Edit: Nevermind, I got it.

In regard to the equation for internal energy:

When work is done by the system on the surroundings, Work is NEGATIVE, right? So U=Q-W

But when work is done by the surroundings on the system, Work is POSITIVE, right? So U=Q+W

 

[SaintJude]

Umm, I think there are different conventions for assigning signs b/w physics and chem. But in all MCAT test prep I've seen

Work done by the system is positive
Work done on the system is negative

 

[mcloaf]

Umm, I think there are different conventions for assigning signs b/w physics and chem. But in all MCAT test prep I've seen

Work done by the system is positive
Work done on the system is negative

No. We're looking at the internal energy of the system, so if the system is doing work on the surroundings it will be losing internal energy, thus the sign of work done by the system on the surroundings is negative.