Final answer:
The energy change in a chemical reaction, represented as ΔH, is primarily due to the difference in bond energies between reactants and products, not changes in atomic nuclei or kinetic energy.
Step-by-step explanation:
The correct statement that explains the source of the energy change in a chemical reaction is: The main contribution to ΔH is the difference in the bond energies of reactants and products. During a chemical reaction, bonds in the reactants are broken and new bonds in the products are formed. The enthalpy change (ΔH), which can be either absorbed or released, is determined by the bond dissociation energies of the reactants and products.
It's important to note that this energy change is not due to changes in the nuclei of the atoms but rather in the electrons' arrangements. Also, ΔH is not primarily about the kinetic energy of the reactants and products or from increased or decreased repulsions between electrons. Essentially, if it takes more energy to break bonds than is released when forming new bonds, the reaction is endothermic (positive ΔH), whereas if more energy is released during bond formation than is required to break the initial bonds, the reaction is exothermic (negative ΔH).