The enthalpy of formation of ethane, ethylene and benzene from the gaseous atoms are -2839.2, -2275.2 and `-5506" kJ mol"^(-1)` respectively. Calculate the resonance energy of benzene. The bond enthalpy of `C-H` bond is given as equal to +410.87 kJ/mol.

Answer

`-23.68` kJ/mol

Explanation

(i) `2C+6H rarr CH_(3)-CH_(3)" "DeltaH=-2839.2`
`-2839.2=0-[(410.87xx6)]+C-C]`
`C-C=373.98`
(ii) `2C+4H rarr C_(2)H_(4)`
`-22275.2=0-[1643.48+C=C]`
`(C = C)=631.72`
(iii) `6C+6H square rarr C_(6)H_(6)`
`DeltaH_("calculayed")=5482.32`
Resonance energy `=5482.32-5506=-23.68" kJ mol"^(-1)`