[PaulSJ]

My catalysis professor asked which is the activation energy magnitude order. (Units: kJ/mole). Most reactions I have come across have values of 10^4 or more, but I need to find some sort of explanation or argument to support that.
Someone suggested using the Eyring equation to calculate activation delta_G from known reaction time, but activation energy is delta_H.

Any idea?

[mjc123]

There is a wide range of activation energies, but 10⁴ kJ/mole is very high. (Did you mean 10⁴ J/mol?) For common reactions that proceed at a sensible rate at ambient temperature, activation energies tend to be of the order of 10-100 kJ/mol. For a reaction that complies with the rule of thumb that the rate doubles for a 10K increase in temperature, the activation energy is about 50 kJ/mol. (Work that out from the Arrhenius equation.)