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### reaction enthalpy vs reaction internal energy

Posted: Wed Jan 10, 2018 6:11 pm
I don't understand the difference between reaction enthalpy and reaction internal energy. can someone lay out the definitions, also how does that correspond to H and U

### Re: reaction enthalpy vs reaction internal energy  [ENDORSED]

Posted: Wed Jan 10, 2018 6:58 pm
The change in enthalpy of a reaction $\Delta H_{\textup{rxn}}$ is by definition the change in heat $q$ of that reaction under constant pressure conditions (open to the atmosphere).

The change in internal energy of a reaction $\Delta U_{\textup{rxn}}$ is by definition the change in heat $q$ of that reaction under constant volume conditions (in a sealed vessel with rigid walls).