Question

The enthalpy of hydrogenation of cyclohexene is $-119.5KJ/mol$ If enthalpy of hydrogen benzene is $-208.1KJ/mol$ , find the resonance of benzene.

• A. $-150.4KJ/mol$
• B. $-208KJ/mol$
• C. $-508.9KJ/mol$
• D. $-269.9KJ/mol$

Answer 1

The correct option is A $-150.4KJ/mol$

The enthalpy of hydrogenation of cyclohexene $=-119.5kJ/mol$

ie hydrogenation of one $C=C=-119.5kJ/mol$

$\therefore$ Enthalpy of hydrogenation of benzene $=3\times (-119.5)kJ/mol=-358.5kJ/mol$

$\therefore$ Resonance Energy of Benzene

$=△H_{obs}-△H_{cal}$

$=-358.5kJ/mol-(-208.1kJ/mol)$

$=-150.4kJ/mol$