Question

Calculate the enthalpy of hydrogenation of`C_(2)H_(2)(g) ` to `C_(2)H_(4)(g)`.
( Given bond energies `: C-H = 414.0 kJ mol^(-1), C=C= 827.6 kJ mol^(-1), C=C= 606 .0 kJ mol^(-1), H-H = 430 .5 kJ mol^(-1))`

Answer 1

Correct Answer - `-175kJ mol^(-1)`
`H-C-=C-H+H-Hrarr underset(H)underset(|) overset(H) overset(|) (C) = underset(H) underset(|)overset(H) overset(|) (C) `
`Delta_(r)H^(@) =`B.E. ( Reactants ) - B.E. ( Products )
`=[ B.E.(C-=C) + 2 xx B.E. ( C-H) + B.E. (H-H) ] - [ B.E.(C=C) + 4B.E.(C-H)]`
`[827.6+2 xx414.0+ 430 .5]-[606.0 + 4 xx 414.0] = - 175.9 kJ mol^(-1)`