# 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 $\text{Cl-Cl}$ bond per mole of $C {l}_{2}$ molecules.

On the other hand, when a $\text{Cl-Cl}$ bond is formed, 243 kJ of energy are released per mole of $C {l}_{2}$ molecules.

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

Therefore, the answer is B) - the formation of a $\text{Cl-Cl}$ bond will release 243 kJ per mole of $C {l}_{2}$ formed.