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.