Calculate the bond energy of C-H bond, given that the heat of formation of CH​4, heat of sublimation of carbon and heat of dissociation of H2 are -74.8, +719.6 and 435.4 kJ mol-1 respectively. (5 marks)

Dear Student,
GIVEN:
 Heat of sublimation                                        C(s)C(g)                            H= 719.6 KJ Heat of dissociation of H                               2H24H                              H=   2×( +435.4)KJ  Heat of formation of C-H bond energy  C(g) +4H4C-H              H=4× x Heat of formation of methane                     4C-H CH4                    H= -74.8 KJ 
Heat of formation of methane=  algebraic sum of all heat changes
-74.8= 719.6 +870.8 +4x4x= -74.8-719.6-870.8x= -416.4 KJ
Negative sign shows that the energy is released during bond formation
Bond energy of C-H bond= 416.4KJ 
Regards!

 

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