Question

Which of the following statements is true for an exothermic reaction?

The products have higher potential energy than the reactants, and the enthalpy change is negative.
The products have higher potential energy than the reactants, and the enthalpy change is positive.
The products have lower potential energy than the reactants, and the enthalpy change is negative.
The products have lower potential energy than the reactants, and the enthalpy change is positive.

Answer 1

The enthalpy change for an exothermic reaction is negative because heat is being released, so that takes out two of the responses. Since energy is being released into the surroundings due to the exothermic reaction, the potential energy of the products is lower than that of the reactants. Energy is being put in to make the reaction occur, but then that energy is all being released into the surroundings thus a lower potential energy level for the products

Answer 2

Ans: The products have lower potential energy than the reactants, and the enthalpy change is negative.

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.