## reaction enthalpy vs reaction internal energy [ENDORSED]

RenuChepuru1L
Posts: 58
Joined: Thu Jul 27, 2017 3:00 am

### reaction enthalpy vs reaction internal energy

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

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

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).

Return to “Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)”

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