IIT JEE , AIEEE Forum - Chemistry , Physical Chemistry

sneha_91

calculate the std enthalphy of hydrogenation of C₆H₆ if for C₆H₁₀ std enthalpy of hydrogenation is -28.6kcal/mol.explain why the answer is different from the actual value(-49.8)

is the answer -28.6

sneha_91

please answer

eistien

C6H6 is an aromatic compund therefore it is highly stable and more the stability lesser the heat of hydrogenation thus the experimental value is less than the theoretical value as for the calculation part i will try after some time and explain

hash_include

$C_6H_{10} + H_2 -> C_6H_{12}$
enthalpy of hydrogenation = $-28.6 kcal/mol$

therefore, the amount of energy released when one $C=C$ is broken is -28.6 kcal.

$C_6H_{6} + 3H_2 -> C_6H_{12}$
so, theoretically, the amount of heat released when 3 $C=C$ bonds break should be $3 *(-28.6)$

thus, theoretically, the enthalpy of hydrogenation for benzene is $-85.8 kcal$ .
but because benzene is resonance stabilized, the amount of energy released is less than the theoretical value
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