Question

When the activation energy is zero then the rate constant is equal to?

Answer 1

From the Arrhenius equation in kinetics of reactions,

k=Aexp(−EaRT)k=Aexp⁡(−EaRT)

Which tells us about the temperature dependence on rate constant of a reaction.

Activation energy is dependent on the temperature (as it is the energy difference between the average energy of the reactants and threshold energy, and since the average energy of reactants depends on the temperature, activation energy also should depend on temperature) Is my assumption that activation energy depends on temperature correct?

Moreover, is there any case where activation energy is zero or negative? (like in the case of spontaneous reaction or Ea=0Ea=0) I feel that whenever activation energy is zero, all the molecules undergoing collisions should form products successfully, but this case won't occur.

But when we substitute Ea=0Ea=0, in the Arrhenius equation, we get the result as k=Ak=A, i.e. rate constant will be equal to pre-exponential factor