Advanced Placement (AP) Chemistry Practice Exam

Which statement describes a characteristic of exothermic reactions?

1. The bonds in the products are weaker than those in the reactants

2. Heat is absorbed from the surroundings

3. The reaction results in a temperature drop

4. They typically release heat and have a negative ΔH

The correct answer is: They typically release heat and have a negative ΔH

In exothermic reactions, energy is released into the surroundings, which typically results in a rise in temperature. This release of energy is often associated with the formation of new bonds in the products. When these products are formed, the bonds are generally stronger than those in the reactants, resulting in a negative change in enthalpy (ΔH). The negative ΔH indicates that the system has lost energy to the surroundings, reinforcing the idea that energy is being released during the reaction. Therefore, identifying that exothermic reactions release heat and are characterized by a negative ΔH accurately reflects their nature.