The enthalpy of hydrogenation of cyclohexene is $-119.5 \mathrm{~kJ} \mathrm{~mol}^{-1}$. If resonance…

The enthalpy of hydrogenation of cyclohexene is $-119.5 \mathrm{~kJ} \mathrm{~mol}^{-1}$. If resonance energy of benzene is $-150.4 \mathrm{~kJ} \mathrm{~mol}^{-1}$, its enthalpy of hydrogenation would be
  1. $-208.1 \mathrm{~kg} \mathrm{~mol}^{-1}$
  2. $-269.9 \mathrm{~kg} \mathrm{~mol}^{-1}$
  3. $-358.5 \mathrm{~kg} \mathrm{~mol}^{-1}$
  4. $-508.9 \mathrm{~kg} \mathrm{~mol}^{-1}$

Solution




$=-358.5 \mathrm{~kJ}$
The resonance energy provides extra stability to the benzene molecule so it has to be overcome for hydrogenation to take place. So $\Delta \mathrm{H}=-358.5-(-150.4)=-208.1 \mathrm{~kJ}$ *

Asked in: JEE-TOPICTESTS-CHEMISTRY

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