Why is the reaction H2 + Cl2 → 2HCl exothermic?

In exothermic reactions, more energy is involved when bonds are formed in the products than used to break the bonds reactant.

If the total energy required to break bonds in the reactants is more than the energy released when new bonds are formed in the product, it is known as an endothermic reaction.

Option A and B are wrong because it is not the number of bonds broken or formed that matter. It is the total energy required to break or make bonds that matter in exothermic and endothermic reactions.
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