TS EAMCET 4-Aug-2021 Shift 1 Question Paper

The hydrogenation of benzene forms cyclohexane.

C6H6

Benzene

+3H2⟶

C6H12

Cyclohexane

Enthalpy of hydrogenation of cyclohexene
=−119.5kJ∕mol
∴ Calculated enthalpy of benzene =3×(−119.5)
=−358.5kJ∕mol
Resonance energy of benzene =−150.4kJ∕mol
As we know,
Actual value of enthalpy = Calculated enthalpy
- Resonance energy
∴ Actual value of enthalpy =(−358.5)−(−150.4)
=−208.1kJ∕mol
Hence, the enthalpy of hydrogenation of benzene is
−208.1kJ∕mol.