Why do the products of an exothermic chemical reaction contain less energy than the starting reactants?

• A. Because the products always have more mass than the reactants.
• B. Because energy is absorbed from the surroundings during the reaction.
• C. Because the reactants are always less stable than the products.
• D. Because energy is released to the surroundings during the reaction.

Answer: (D)

Verified step by step guidance

1. Understand that in an exothermic reaction, energy is released to the surroundings, usually in the form of heat.
2. Recall that the total energy of the system includes the chemical potential energy stored in the bonds of reactants and products.
3. Recognize that the reactants start with a certain amount of chemical energy, and during the reaction, some of this energy is released.
4. Since energy is released, the products must have less stored chemical energy than the reactants, making the products more stable.
5. Therefore, the energy difference between reactants and products corresponds to the energy given off to the surroundings, explaining why products contain less energy.