Chemistry Regents Practice Test

In a chemical reaction, what does the difference between the potential energy of the products and reactants represent?

1. Activation energy

2. Total energy change

3. Heat of the reaction

4. Energy conservation

The correct answer is: Heat of the reaction

The difference between the potential energy of the products and reactants in a chemical reaction represents the heat of the reaction. This value indicates the overall change in energy associated with the reaction, known as the enthalpy change (ΔH). When a reaction occurs, bonds are broken in the reactants and new bonds are formed in the products. The potential energy associated with these bonds differs, and the resulting difference reflects whether the reaction is exothermic (releasing heat) or endothermic (absorbing heat). A negative value indicates that the products have lower potential energy than the reactants, which means energy has been released to the surroundings. Conversely, a positive value indicates that energy was absorbed from the surroundings to form the products. The heat of the reaction is a crucial concept in understanding reaction energetics, particularly for predicting the energy changes that occur during chemical transformations.