Question

The enthalpy of hydrogenation of cyclohexene is $-119.5\, kJ\, mol ^{-1}$. If resonance energy of benzene is $-150.4\, kJ\, mol ^{-1}$, its enthalpy of hydrogenation would be

• A. $- 358.5\, kJ\, mol^{-1}$
• B. $- 508.9\, kJ\, mol^{-1}$
• C. $- 208.1\, kJ\, mol^{-1}$
• D. $- 269.9\, kJ\, mol^{-1}$

Answer 1

Answer: (C)

Enthalpy of hydrogenation of benzene
$=3 \Delta( H )_{\text {Hydrogenation }}-( R . E )$
$=3 \times(-119 \cdot 5)-(-150 \cdot 4)=-358 \cdot 5+150 \cdot 4$
$=-208 \cdot 1\, kJ\, mol ^{-1}$