Question

Use the data found in the appendix to determine the values for the O-Cl and the O-F bond energies. (heats of formation of OF₂ and OCl₂ are 24.7 and 80.37 kJ/mol, respectively)

DO-F	kJ/mol
DO-Cl	kJ/mol

Answer 1

Delta Hf OF2 = 24.7 kJ

Delta Hf OCl2=80.37 kJ

Using the bond energies we can find the bond energy value of O-Fand O-Cl bonds as follows

Formula

Delta Hf = [bond energy of reactant] [bond energies ofproduct]

Reaction equation for the OF2

O2 + F2 --- > OF2 deltaHf = 24.7kJ/mol

Delta Hf = [bond energy of reactant] [bond energies ofproduct]

= [( O=O*1)+(1*F-F)]-[2*O-F]

24.7 = [ (1/2*495) +(154*1)]-[2*O-F]

24.7 = 401.5 [2*O-F]

24.7 401.5 = [2*O-F]

-376.8 = - 2* O-F

-376.8 / -2 = O-F

188.4 kJ/mol = O-F

Therefore bond energy of the O-F bond is 188.4kJ/mol

Now lets calculate the bond energy of the O-Cl bond

Reaction equation for the OCl2

O2 + Cl2 --- > OCl2delta Hf = 80.37kJ/mol

Delta Hf = [bond energy of reactant] [bond energies ofproduct]

= [( O=O*1)+(1*Cl-Cl)]-[2*O-Cl]

80.37 = [ (1/2*495) +(239*1)]-[2*O-Cl]

80.37 = 486.5 [2*O-Cl]

80.37 486.5 = [2*O-Cl]

-406.13 = - [2* O-Cl]

-406.13 / -2 = O-Cl

203.1 kJ/mol = O-Cl

Therefore bond energy of the O-Cl bond is 203.1kJ/mol