Which statement is true about the enthalpy change contributions in bond-breaking and bond-forming?

Which statement is true about the enthalpy change contributions in bond-breaking and bond-forming?

• A. The energy required to break bonds in reactants
• B. The energy absorbed to break bonds in products
• C. The energy released when bonds form in the products
• D. The energy required to rearrange electrons without changing bonds

Answer: (C)

Enthalpy change in a reaction comes from two opposing energy terms: the energy you must input to break bonds in the reactants (endothermic) and the energy you release when new bonds form in the products (exothermic). The overall ΔH is the energy broken minus the energy formed. The statement that best captures one of these contributions is the energy released when bonds form in the products. This released energy is the exothermic part that lowers the overall enthalpy change and often makes the reaction heat out. The energy required to break bonds in reactants is also part of the picture, but by itself it doesn’t fully describe how the enthalpy change is determined. The other choices describe situations that aren’t the primary contributors to ΔH in the typical bond-energy framework (for example, breaking bonds in products or rearranging electrons without changing bonds).

Enthalpy change in a reaction comes from two opposing energy terms: the energy you must input to break bonds in the reactants (endothermic) and the energy you release when new bonds form in the products (exothermic). The overall ΔH is the energy broken minus the energy formed. The statement that best captures one of these contributions is the energy released when bonds form in the products. This released energy is the exothermic part that lowers the overall enthalpy change and often makes the reaction heat out. The energy required to break bonds in reactants is also part of the picture, but by itself it doesn’t fully describe how the enthalpy change is determined. The other choices describe situations that aren’t the primary contributors to ΔH in the typical bond-energy framework (for example, breaking bonds in products or rearranging electrons without changing bonds).