What chemical theory supports the use of energies for endothermic reactions as approximations for the activation energy of a reaction?

Chemical kinetics

Explanation:

According to the theory that governs the study of kinetics, in a given system, reagents tend to collide to form products.

However, this collision, or shock, must be effective in order to generate the energy necessary to initiate the reaction. The minimum amount of energy required for a reaction to occur is called activation energy.

In endothermic reactions, which are those that absorb energy, the activation energy is greater than in exothermic reactions, which are those that release energy.