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Free Energy help

  1. Jan 22, 2008 #1
    It's thermo.. so I just posted it in the physics forums

    but.. a free energy diagram is supposed to represent G right?

    We normally conclude whether a rxn is endo/exothermic depending on whether the product is at a "lower" or higher energy than the reactants just by looking at the diagram


    But how can we do that? especially if Delta G = Delta H - (T * Delta S)
    Free energy depends on Entropy and Temperature as well

    A "negative" change in free energy surely does not necessarily mean an exothermic reaction.... but somehow, we are able to conclude whether something is exo/endo simply by looking at a free energy diagram.. how?

    Attached Files:

  2. jcsd
  3. Jan 22, 2008 #2


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    Staff: Mentor

    The diagram you have there doesn't have any numbers on it, but if it did it would be valid for only one set of initial conditions.

    I'm not sure I understand your last sentence. A negative delta G is exothermic because it means energy is released. The initial hump there doesn't have anything to do with if the final result is exothermic or endothermic - it is just the required activation energy (in this case, it looks like the energy required to disassociate the constituents of the compound).
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