<u>Ans: The products have lower potential energy than the reactants, and the enthalpy change is negative. </u>
In general, chemical reactions can be broadly classified into two categories:
1) Exothermic
2) Endothermic
Exothermic reactions proceed with the evolution of heat. Here, the reactants have a higher potential energy which is released as the reaction progresses to form products. Consequently, the products are in a lower energy state. Since energy is released, the enthalpy change will be negative.
In contrast, endothermic reactions proceed with the absorption of heat. Here,the products will be in a higher energy state. Since energy is absorbed, the enthalpy change will be positive.