Question

Heat of dissociation of benzene to elements is ${\text{5535 KJ mol}}^{-1}$. The bond enthalpies of $C-C,C=C$ and $C-H$ are $347.3,615.0$ and $416.2$ KJ respectively. Resonance energy of benzene is:

• A. $\text{1.51 KJ}$
• B. $\text{15.1 KJ}$
• C. $\text{151 KJ}$
• D. $\text{1511 KJ}$

Answer 1

The correct option is C $\text{151 KJ}$

Experimental heat of atomisation of benzene is $5535KJmo{l}^{-}1$

Theoretical heat of atomisation breaking of $3$ $(C-C)$ bonds$3$ $(C=C)$ bonds and $6$ $(C-H)$ bonds is $3\times 347.3+3\times 615.0+6\times 416.2$

$=5384.1KJmo{l}^{-}1$

Hence resonance energy of benzene$=(5535-5384)KJ$

$=151KJ$