question_answer

Bond dissociation enthalpy of \[F-F\] bond is less than that of \[\text{C}l\,\text{-}\,\text{C}l\]bond. Explain.

Answer:

                Bond length of \[F-F\] bond (143 pm) is less than that of \[\text{C}l\,\text{-}\,\text{C}l\] bond (199 pm). Therefore, bond dissociation enthalpy or bond energy of \[{{F}_{2}}\] is expected to be more than that of \[\text{C}{{l}_{2}}\]. But actually it is less. This is an account of greater force of repulsion in the non-bonded (lone) electron pairs in the molecule of \[{{F}_{2\,}}\,(:\underset{.\,\,\,\,.}{\overset{.\,\,\,\,.}{\mathop{F}}}\,:\underset{.\,\,\,.}{\overset{.\,\,\,.}{\mathop{F}}}\,:)\] than in \[C{{l}_{2}}\] as a result of which the bond cleavage is easier.