IIT/JEE Chemistry Practice #27: Resonance Energy

The video tutorial explores the concept of resonance energy in benzene. It begins by introducing the standard molar enthalpies of formation for cyclohexane and benzene, and the enthalpy of hydrogenation for cyclohexene. The tutorial explains how to estimate the resonance energy of benzene by comparing expected and actual enthalpy changes during hydrogenation. The expected enthalpy is calculated by tripling the enthalpy of hydrogenation of cyclohexene, while the actual enthalpy is derived from standard molar enthalpies of formation. The difference between these values gives the resonance energy, highlighting benzene's lower energy due to aromaticity.

What is the standard molar enthalpy of formation for benzene liquid at 25 degrees Celsius?

• 205 kJ/mol

• 49 kJ/mol

• 156 kJ/mol

• 119 kJ/mol

How much energy is released when a single π bond on cyclohexene is hydrogenated?

• 119 kJ/mol

• 357 kJ/mol

• 205 kJ/mol

• 156 kJ/mol

What is the expected enthalpy change when benzene is fully hydrogenated?

• 119 kJ/mol

• 152 kJ/mol

• 357 kJ/mol

• 205 kJ/mol

What is the actual enthalpy change when benzene is completely hydrogenated to cyclohexane?

• 357 kJ/mol

• 205 kJ/mol

• 152 kJ/mol

• 119 kJ/mol

How much lower is benzene's energy due to resonance compared to a system with three isolated π bonds?

• 119 kJ/mol

• 357 kJ/mol

• 205 kJ/mol

• 152 kJ/mol