Final answer:
Bond dissociation energies are used to approximate the energy changes in a chemical reaction, which are necessary for calculating the enthalpy change. This estimate helps to understand whether the reaction is endothermic or exothermic.
Step-by-step explanation:
Bond dissociation energies can be used to approximate the energy changes taking place during chemical reactions in which bonds are being broken in reactants and formed in products. These energy changes can be used to calculate the enthalpy change or heat of reaction for a chemical process.
Bond dissociation energy represents the energy required to break a bond in 1 mole of a gaseous substance, which is provided or absorbed during chemical reactions. When bonds are broken, this process requires energy, making it endothermic. Conversely, forming bonds releases energy, making this process exothermic.
The bond energy is indicated by the bond enthalpy, which is conventionally measured as the energy needed to break a chemical bond. For calculating enthalpy changes, the bond energies of broken and formed bonds are summed, shown by the equation ΔH = Σ bond energies of broken bonds – Σ bond energies of formed bonds.
This can help to determine whether a chemical process is endothermic or exothermic. However, it's important to note that while bond energies provide a good estimate, they are an average and actual values can differ within different molecules.