If a `298K` the bond energies of `C-H,C-C,C=C` and `H-H` bonds are respectivly `414, 347, 615KJmol^(-1)` , the vlaue of enthalpy change for the reaction
`H_(2)C=CH_(2)(g)+H_(2)(g)+H_(2)(g)rarrH_(3)C-CH_(3)(g)` at `298K` will be

Options

A. `+250KJ`
B. `-250KJ`
C. `+125KJ`
D. `-125KJ`

Answer

B

Explanation

`CH_(2)=CH_(2)(g)+H_(2)(g)rarrH_(3)C-CH_(3)(g)`
`4E_(C-H)implies 414xx4=16566E_(C-H) implies 414xx6=2484`
`1E_(C=C) implies 615xx1=61E_(C-C) implies 347xx1=347`
`1E_(H-H) implies 435xx1=435`
`4DeltaH_(C-H)+DeltaH_(C=C)+DeltaH_(H-H)=2706rarr`
`6DeltaH_(C-H)+DeltaH_(C-C)=2831`
`DeltaH=2706-2831=-125KJ`