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Reactants have a higher enthalpy

  1. Apr 8, 2013 #1
    Am I right in saying that, in an exothermic reaction for example, the reactants have a higher enthalpy, and the products have a lower enthalpy, as seen from the energy profile diagram.
    But the reactants have a lower bond enthalpy, and the products have a higher bond enthalpy, because a lower amount of energy is required to break the bonds in the reactants, but a higher amount of energy is released when the new bonds are formed. This just confused me as I thought enthalpy and bond enthalpy were the same thing!
  2. jcsd
  3. Apr 10, 2013 #2


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    During the course of reaction, the internal energy, and by extension, enthalpy, changes.

    For e.g. During a reaction, the energy first increases to a certain maximum level (Difference in energy is called Activation Energy) then it comes down. (You know the bell-shaped graph)

    The reactions doesn't takes place in arithmetic method. Even if burning is exothermic, it doesn't mean that we do not have to provide energy to do it.
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