The Cl-Cl bond energy is 243 kJ/mol. Therefore the formation of a single bond between chlorine atoms ? A) should require the absorption of 243 kJ per mole of #Cl_2# formed. B) should result in the release of 243 kJ per mole of #Cl_2# formed.

1 Answer
Apr 24, 2015

The bond energy, or bond enthalpy, expresses the energy needed to break a chemical bond, that's why it will always be listed as a positive value.

In your case, 243 kJ of energy are required to break the #"Cl-Cl"# bond per mole of #Cl_2# molecules.

On the other hand, when a #"Cl-Cl"# bond is formed, 243 kJ of energy are released per mole of #Cl_2# molecules.

Bond making is an exothermic process, while bond breaking is an endothermic process.

Therefore, the answer is B) - the formation of a #"Cl-Cl"# bond will release 243 kJ per mole of #Cl_2# formed.