State the role of activated complex in a reaction and state its relation with activation energy?

Activated complex is the intermediate compound formed by reactants, which is highly unstable and readily changes into product. Those reactants which possess activation energy and collide in proper orientation can form activated complex which can easily form products.
Lower the activation energy, more easily activated complex will be formed and faster will be the reaction.
Activation energy = energy of activated complex - energy of reactants
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