relation between delta H and delta U  [ENDORSED]

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relation between delta H and delta U

Postby RenuChepuru1L » Wed Jan 10, 2018 6:10 pm

I'm confused by a part in the textbook that says "delta H is less negative(more positive) than delta U for reactions that generate gases:less energy can be obtained from a reaction as heat at constant pressure than at constant volume, because the system must use some energy to expand to make room for the reaction products." aren't these two sentences in direct opposition to each other?

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Re: relation between delta H and delta U  [ENDORSED]

Postby Chem_Mod » Wed Jan 10, 2018 6:54 pm

Remember that the more negative the enthalpy change, the more enthalpy (heat at constant pressure) is formed. The description says the change in enthalpy is less negative than the change in internal energy. Thus, less heat was evolved because some went of that energy went to expand against the atmosphere.

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

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