Using bond enthalpies (symbolized by `epsilon`) an estimated value of `DeltaH^(@)` for the reaction
`H_(2)C=CH_(2)(g)+H_(2)(g)rarrCH_(3)-CH_(3)(g)` would be

Options

A. `epsilon_(C=C)+epsilon_(H-H)-2epsilon_(C-H)-epsilon_(C-C)`
B. `epsilon_(C=C)+epsilon_(H-H)-6epsilon_(C-H)-epsilon_(C-C)`
C. `epsilon_(C=C)+epsilon_(H-H)-4epsilon_(C-H)-epsilon_(C-C)`
D. `epsilon_(C=C)+epsilon_(H-H)-4epsilon_(C-H)-epsilon_(C-C)`

Answer

D

Explanation

`B.E.` required to break one `C=Cimplies epsilon_(C=C)`
`B.E.` required to break one `H-Himplies epsilon_(H-H)`
`B.E.` released in the formation of one `C-C=-epsilon_(C-C)`
`B.E.` released in the formation of two `C-H` bonds `=-2epsilon_(C-H)`
`:. DeltaH_(Rxn)^(@)=epsilon_(C=C)+epsilon_(H-H)-2_(epsilon_(C-H))-epsilon_(C-C)`