Question

Heat of formation of C2H4 = 12.5 Kcal Heat of atomization of C =171 Kcal Heat of atomization of H = 52.1 Kcal; Bond energy of C-H = 99.3 Kcal Find the C=C bond energy.

Answer 1

WE need to take 2 atomization of C+ 
4 atomization of H+
4 bond energy pf C-H
1 heat formation of C2H4

2 x 171 + 4 x 52.1 - 4 x 99.3 - K = 12.5
k= 140.7 Kcal

Answer 2

"Heat of atomisation of c =171 kcal

Heat of atomisation of H = 52.1 kcal

Bond energy C-H = 99.3 Kcal

To take 2 atomization of C+

4 atomization of H+

4 bond energy of C-H

1 heat formation of C2H4

2 x 171 + 4 x 52.1 - 4 x 99.3 - K = 12.5

K = 140.7 Kcal

"