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In solution phase, the activation energy of a reaction is usually determined through the study of kinetics and the Arrhenius equation. However, I am confused by the notation, and have trouble interpreting the Ea term, almost universally called "activation energy". Is it free energy? Or is it enthalpy? This is important, because I want to compare some experimental and theoretical values and in the output of quantum chemistry software the differences between energy/enthalpy/free energy are quite clear, and I want to be sure that I compare the right ones.

So my question is: The Ea calculated via the Arrhenius eq. is the enthalpy change going from the reactants to the transition state, or is it the free energy change?


marked as duplicate by Community Oct 27 '15 at 20:44

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