Standard enthapies of formation are not always like bond enthalpies.Explain
To understand why standard enthalpies of formation are not always like bond enthalpies, let's first define what each term represents.
Standard enthalpy of formation (ΔHf°) is the change in enthalpy that occurs when one mole of a substance is formed from its constituent elements, with all reactants and products in their standard states (usually at 25°C and 1 atm).
Bond enthalpy, on the other hand, is the average amount of energy required to break a particular type of bond in one mole of gaseous molecules, averaged over a range of different compounds.
While bond enthalpies are related to the energy required to break specific types of bonds, standard enthalpies of formation take into account the enthalpy changes associated with the formation of an entire compound, not just its individual bonds. This means that standard enthalpies of formation consider factors beyond bond energies, such as changes in electronic configurations, lattice energies, and intermolecular forces.
Moreover, bond enthalpies are averages calculated from a range of different compounds that contain the same bond type. These averages can vary depending on the nature of the other atoms involved and the chemical environment. On the other hand, standard enthalpies of formation are specific to a particular compound, providing a more accurate representation of the enthalpy change during its formation.
To summarize, while bond enthalpies are useful for estimating the energy required to break specific types of bonds, standard enthalpies of formation take into account the overall formation of a compound, considering all the relevant energetic factors. Therefore, standard enthalpies of formation are not always equivalent to bond enthalpies.