Question

What do you understand by the activation energy of a reaction?

Answer 1

Activation energy (`E_"a"`) is the minimum energy required for a chemical reaction to occur.

According to collision theory, molecules are in constant motion and colliding with each other. Some molecules move fast; some move slowly.

Only those collisions that have enough energy to break old bonds and form new ones will result in a reaction.

The minimum energy that will allow this to happen is the activation energy.

At this point, the colliding molecules have formed a transition state. Old bonds are partially broken, and new bonds have partially formed.

The transition state is at the top of an energy hill. It can either continue forming the new bonds and go on to products, or it can re-form the old bonds and return to reactants.

`E_"a"` is thus the potential energy barrier that separates reactants from products.