Which of the following best describes the law of conservation of energy during a reaction?

The law of conservation of energy states that energy cannot be created or destroyed in an isolated system; it can only be transformed from one form to another. In the context of a chemical reaction, this means that the total amount of energy present before the reaction must equal the total amount of energy present after the reaction.

When a chemical reaction occurs, the energy stored in the chemical bonds of the reactants is transformed. This energy may be released or absorbed as the bonds are broken and new bonds are formed in the products. This transformation is what allows for the processes of releasing heat (exothermic reactions) or absorbing heat (endothermic reactions). Therefore, describing energy as transformed from reactants to products accurately reflects the principles underlying the law of conservation of energy during a chemical reaction.