If in a reaction the energy released in forming bonds is greater than the energy required to break bonds, what is the overall energy change and is the reaction exothermic or endothermic?

• A. Positive energy change (endothermic)
• B. Zero energy change
• C. Negative energy change (exothermic)
• D. The energy change cannot be determined from the information given

Answer: (C)

When more energy is released by forming new bonds than is used to break the old ones, the total energy change is negative, and the process is exothermic. The overall change is found from ΔH = energy broken − energy formed. If the energy formed is greater, ΔH is negative, so the reaction gives off energy to its surroundings. That’s why the correct description is a negative energy change and exothermic.