Which statement about energy in a chemical reaction is correct?

• A. Energy increases during the reaction
• B. The total energy before and after is the same
• C. Energy is created during the reaction
• D. Energy decreases during the reaction

Answer: (B)

Conservation of energy governs chemical reactions: energy can be transformed but not created or destroyed. In a reaction, bonds in reactants store energy, breaking those bonds requires input energy, and forming new bonds releases energy. The net energy change shows up as heat, light, or a temperature change in the surroundings, but the total energy of the system plus its surroundings stays the same. So the amount of energy present before the reaction equals the amount present after, just redistributed between reactants, products, and the surroundings. Energy isn’t inherently increasing or decreasing during the reaction itself; what changes is how that energy is stored or released, with the surroundings taking up or supplying the difference. This is why the statement that the total energy before and after remains the same correctly reflects energy conservation. Saying energy is created or destroyed would violate this fundamental principle.