Thermodynamics and Thermochemistry
14.0 Bond Energy or Bond Enthalpies
14.0 Bond Energy or Bond Enthalpies
The amount of energy required to break one mole of a bond of a particular type between the atoms in the gaseous state, i.e to separate the atoms in the gaseous state under 1 atm, pressure and the specified temperature is called bond dissociation energy.
Example: $$H - H\left( g \right) \to 2H\left( g \right),\quad \quad \quad \Delta H = + 433\;kJ\;mo{l^{ - 1}}$$
$$Cl - Cl\left( g \right) \to 2Cl\left( g \right),\quad \quad \quad \Delta H = + 242.5\;kJ\;mo{l^{ - 1}}$$
$$H - Cl\left( g \right) \to H\left( g \right) + Cl\left( g \right)\quad \quad \Delta H = + 431\;kJ\;mo{l^{ - 1}}$$
The bond dissociation energy of a diatomic molecule is called bond energy. When more than one bond of the same kind are present in a compound, then the average bond dissociation energy required to break each bond in a compound is called bond energy.
