Bondy Enthalpy Accuracy

[Ashley Garcia 2L]

When calculating standard reaction enthalpies, why is using bond enthalpies the least accurate method?

[Andres Reynoso 1J]

Using bond enthalpies is the least accurate method to calculate standard reaction enthalpies because bond enthalpies are averages of the dissociation enthalpies of bonds from several different molecules. Essentially, they are the least accurate because it is an average, where other methods are more precise.

[ConnorThomas2E]

The bond enthalpy method actually takes into account mean bond enthalpy. In different molecules, the amount of atoms attached to the central molecule, lone pair electrons, and etc. affect the strength of bonds. As a result, the same bond between two atoms in different molecules will have a different bond enthalpy. The mean bond enthalpy gives the average amount of enthalpy for these bonds, not a precise number, therefore making this method not as accurate.

[Tasnia Haider 1E]

in addition to what others said, bond enthalpies for diatomic molecules are the only exact calculations. Every other bond enthalpy is an average.