From the following bond energies: `H--H` bond energy: `431.37KJmol^(-1)`
`C=C` bond energy: `606.10KJmol^(-1)`
`C--C` bond energy: `336.49KJmol^(-1)`
`C--H` bond energy: `410.50KJmol^(-1)`
Enthalpy for the reaction will be:
`overset(H)overset(|)underset(H)underset(|)(C)=overset(H)overset(|)underset(H)underset(|)(C)+H-H to Hoverset(H)overset(|)underset(H)underset(|)(C)-overset(H)overset(|)underset(H)underset(|)(C)-H`

Options

A. `1523.6 KJ "mol"^(-1)`
B. `-243.6 KJ "mol"^(-1)`
C. `-120.0 KJ "mol"^(-1)`
D. `553.0 KJ "mol"^(-1)`

Answer

C

Explanation

For reaction,
`underset(H)underset(|)C=underset(H)underset(|)C+H-H to H-underset(H)underset(|)C-underset(H)underset(|)C-H`
`DeltaH_("reaction")`
`=sumBE_("reaction")-sumBE_("product"), [BE` =bond energy `]`
`DeltaH_(r)=[4xxBE_(C-H)+1xx BE_(C=C)+ 1xxBE_(H-H)]`
`-[6xx BE_(C-H)+1 xx BE_(C-C)]`
`=(4xx410.50 + 1xx606.1 + 1xx 431.37)`
`-[(6xx410.50)+(1xx336.49)] KJ "mol"^(-1)`
`=[1642 + 606.1 + 431.37]-[2463 + 336.49] KJ "mol"^(-1)`
`=[2679.47] -[2799.49] JK "mol"^(-1)=-120.0 KJ "mol"^(-1)`