The standard molar enthalpies of formation of cyclohexane (l) and benzene (l) at `25^(@)C` are `-156` and `+49 kJ mol^(-1)`, respectively. The standard enthaly of hydrogenation of cyclohenxene (l) at `25^(@)C` is `-119 kJ mol^(-1)` Use this data to estimate the magnitude of the resonance enegry of benzene.

Explanation

Enthalpy of formation of 3 carbon-carbon double bonds

`=-156-(+49) kJ`
`=-205 kJ`.
Given that,

Theoretical enthalpy of formation of 3 double bonds in benzene ring
`=3xx(-119) kJ`
`=-357 kJ`
`:.` resonance energy of benzene `=-357-(-205) kJ`
`=-152 "kJ mole"^(-1)`.