Question

H(f) Cl= 121.3 kj
H(f) C= 716.7
H(f) CCl4= -95.7


calculate the average molar bond enthalpy of the carbon-chlorine bond in a CCl4 molecule.

I have tried to figure it out and keep getting the wrong answer. Please help!

Answer 1

I would do this but you should confirm. I looked up the C-Cl bond energy in a text I have and it lists 330 kJ/mol.
C + 4Cl ==> CCl4
dHrxn = (dHf products) - (n*dHf reactants)
dHrxn = (-95.7) - (716.7 + 4*121.3) = about -1300 and that divided by 4 = about -325 or so. Then you change the sign since you want the reverse reaction. Looks reasonable to me. If I were doing it I would write in +324.4 kJ/mol