ThermochemistryHard

Question

The standard molar enthalpies of formation of cyclohexane (l) and benzene(l) at 298 K are −156 and +49 kJ/ mol, respectively. The standard enthalpy of hydrogenation of cyclohexene (l) at 298 K is −119 kJ/mol. Use these data to estimate the magnitude of the resonance energy of benzene.

Options

A.152 kJ/mol
B.250 kJ/mol
C.12 kJ/mol
D.86 kJ/mol

Solution

$\Delta H = ( - 156) - (49 + 0) = - 205\text{ kJ}$

$\therefore$Magnitude of resonance energy = $3 \times 119 - 205 = 152\text{ kJ}$

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