Strength of Covalent Bonds

1. Bond Enthalpy is always positive

1.1. Energy is always required to break chemical bonds.

1.2. Energy is released when a bond forms between 2 gaseous atoms or molecules fragments.

1.3. The greater the bond enthalpy, the stronger the bond (less tendency for reactions).

2. ΔHrxn = Σ(bond enthalpies of bonds broken) – Σ (bond enthalpies of bonds formed).

3. If ΔHrxn = positive value

3.1. The reaction is endothermic

4. If ΔHrxn = negative value

4.1. The reaction is endothermic

5. Bond Enthalpy

5.1. In chemistry, bond energy, also called the mean bond enthalpy or average bond enthalpy is the measure of bond strength in a chemical bond.

5.2. D(bond type) = Represent bond enthalpies

5.3. D = the energy required to break the diatomic molecule into its component atoms.

6. Average Bond Energies (kJ/mol)

7. Examples