Answer:
Bond energy of carbon-fluorine bond is 485 kJ/mol
Explanation:
Enthalpy change for a reaction, is given as:
![\Delta H_{rxn}=\sum [n_{i}\times (E_{bond})_{i}]-\sum [n_{j}\times (E_{bond})_{j}]](https://tex.z-dn.net/?f=%5CDelta%20H_%7Brxn%7D%3D%5Csum%20%5Bn_%7Bi%7D%5Ctimes%20%28E_%7Bbond%7D%29_%7Bi%7D%5D-%5Csum%20%5Bn_%7Bj%7D%5Ctimes%20%28E_%7Bbond%7D%29_%7Bj%7D%5D)
Where
and
represents average bond energy in breaking "i" th bond and forming "j" th bond respectively.
and
are number of moles of bond break and form respectively.
In this reaction, one mol of C=C, four moles of C-H and one mol of F-F bonds are broken. One mol of C-C bond, four moles of C-H bonds and two moles of C-F bonds are formed
So, ![-549kJ=(1mol\times 614kJ/mo)+(4mol\times E_{C-H})+(1mol\times 154kJ/mol)-(1mol\times 347kJ/mol)-(4mol\times E_{C-H})-(2mol\times E_{C-F})](https://tex.z-dn.net/?f=-549kJ%3D%281mol%5Ctimes%20614kJ%2Fmo%29%2B%284mol%5Ctimes%20E_%7BC-H%7D%29%2B%281mol%5Ctimes%20154kJ%2Fmol%29-%281mol%5Ctimes%20347kJ%2Fmol%29-%284mol%5Ctimes%20E_%7BC-H%7D%29-%282mol%5Ctimes%20E_%7BC-F%7D%29)
or, ![-549kJ=(1mol\times 614kJ/mo)+(1mol\times 154kJ/mol)-(1mol\times 347kJ/mol)-(2mol\times E_{C-F})](https://tex.z-dn.net/?f=-549kJ%3D%281mol%5Ctimes%20614kJ%2Fmo%29%2B%281mol%5Ctimes%20154kJ%2Fmol%29-%281mol%5Ctimes%20347kJ%2Fmol%29-%282mol%5Ctimes%20E_%7BC-F%7D%29)
or, ![E_{C-F}=485kJ/mol](https://tex.z-dn.net/?f=E_%7BC-F%7D%3D485kJ%2Fmol)
So bond energy of carbon-fluorine bond is 485 kJ/mol
C6H5 is the molecular formula for Phenyl.