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Activation energy

In chemistry, the minimum amount of energy that is required to activate atoms or molecules to a condition in which they can undergo chemical transformation or physical transport.


Constant Ea in the exponential part of the Arrhenius rate equation (also known as Arrhenius law or Arrhenius equation) associated with the minimum energy difference between the reactants and an activated complex, (transition state which has a structure intermediate to those of the reactants and the products) or with the minimum collision energy between molecules that is required to enable a reaction.

Apparent activation energy: In practice, reaction rates are often determined by physical processes (e.g. mass flow, diffusion, mass transfer area) as well as by chemical processes. The activation energy observed in these cases is called the apparent activation energy.


  •  HarsNet, HarsBook, A technical guide for the assessment of highly reactive chemical systems, DECHEMA e.V., Frankfurt, 2002.

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