Single Bond Energies

Related Resources • Physical Chemistry & Thermodynamics • Make an Endothermic Reaction • Endothermic & Exothermic Reactions • Worked Heats of Formation Problems • Laws of Thermochemistry • Worked Enthalpy Change Problems  Related Tables • Chemistry Charts & Tables • Heats of Formation - Ions • Heats of Formation - Compounds • Valences of the Elements • Electronic Configuration of the Elements

Knowing the values for bond energy helps us to predict whether a reaction will be exothermic or endothermic. For example, if the bonds in the product molecules are stronger than the bonds of the reactant molecules, then the products are more stable and have a lower energy than the reactants, and the reaction is exothermic. If the reverse is true, then energy (heat) must be absorbed in order for the reaction to occur, making the reaction endothermic. In this case, the products have a higher energy than the reactants. Bond energies may be used to calculate change in enthalpy, DH, for a reaction by applying Hess's Law. DH can be obtained from the bond energies only when all of the reactants and products are gases.