Question

4. Describe in detail the relationship between chemical bonds and energy. What must be true of the bonds for a reaction to be endothermic, and what must be true for the reaction to be exothermic?

Answer 1

When a bond is formed, the energy is released. Also, it must be supplied when the bond is broken.
In an endothermic reaction, the energy required to break the bond in the reactants must be greater than the energy released forming the bond in the product.
In an exothermic reaction more energy is released in forming  the bonds on the product than is absorbed to break the bonds in the reactants.