Answer
Plot a represent an exothermic reaction. The reactants have weaker bonds. In plot b, reactants must gain potential energy from the surroundings such enthalpy.
Work Step by Step
An exothermic reaction represents a decrease in potential energy from reactants to products. Therefore, plot A which depicts a loss of potential energy from reactants to products represents an exothermic reaction.
Weaker bonds are associated with higher potential energies. Therefore, the reactants in plot a have weaker bonds as they have a higher potential energy.
By the Law of Conservation of Energy, the reactants must receive the energy from the surroundings in an endothermic process.
