In a potential energy diagram, which statement is true for an exothermic reaction?

• A. Reactants have more potential energy than products
• B. Reactants have less energy than products
• C. Products have more energy than reactants
• D. The diagram does not show energy changes

Answer: (A)

In a potential energy diagram, an exothermic reaction releases energy, so the system ends at a lower energy than where it began. This means the reactants sit at a higher energy level and the products at a lower energy level, with the energy difference corresponding to heat released to the surroundings. The diagram also shows an activation energy barrier that must be overcome before the reaction proceeds, but once past that peak, the final energy is lower than the initial energy. Therefore, the true statement is that reactants have more potential energy than products. The other possibilities would either require energy absorption (endothermic) or show no energy change, which isn’t the case here.