Question

Why a reaction cannot have -ve activation energy?

Answer 1

Dear Student,

Activation energy is the energy required by reaction to reach the threshold energy (energy barrier). It is defined as the least possible amount of energy (minimum) which is required to start a reaction.
So, it is positive because it needs to be provided to the reactants in any form such as heat. It may be small or large in magnitude.

In certain cases, where reaction rates decrease on increasing temperature. in those cases activation energy would be negative. Occurrence of such reactions is very low. Such reactions are considered barrierless.

But in maximum cases, activation energy is positive.

Regards.