The temperature coefficient in relation to thermodynamic quantities

Consider a reaction in a perfect gas mixture. As shown previously the following relation is compatible with thermodynamics  

On the other hand, if partial prisssures had been used in place of concentrations for the purpose of defining the velocity constants we should have obtained (15-24) 

It follows from (15 23) and (15 25) that the Arrhenius activation energy is either an internal energy or an enthalpy, according to whether the velocity constants are expressed in terms of concentrations or partial pressures respectively. The use of concentrations is the more usual. 

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