Hello. I am a thermodynamics novice trying to gain a better understanding of state functions, particularly enthalpy.(adsbygoogle = window.adsbygoogle || []).push({});

I understand that enthalpy is defined as

"A measure of the total energy of a thermodynamic system, including internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure."

The equation:

ΔH=ΔU(internal energy) + ΔPV

confuses me b/c

ΔU= q(heat added) - w(work done by system on environment)

so

ΔH really means:

ΔH=q - w + ΔPV

There are two terms of work (w and ΔPV) and b/c of the opposite sign, they cancel out, leaving only q. This means ΔH= q which is at odds with the accepted definition of enthalpy. Where did I mess up?

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# Why does the enthalpy equation include work (PV term) twice?

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