The enthalpy of combustion at 25°C of (g), cyclohexane(l) and cyclohexene(l) are -241, -3920 and -3800 kJ/mol, respectively. The enthalpy of hydrogenation of cyclohexene(l) is

Question

The enthalpy of combustion at 25°C of $H_2$(g), cyclohexane(l) and cyclohexene(l) are -241, -3920 and -3800 kJ/mol, respectively. The enthalpy of hydrogenation of cyclohexene(l) is

Prashant Kotian · Accepted Answer

Correct answer: A. The hydrogenation reaction of cyclohexene is: C6H10(l) + (g) -> C6H12(l). By Hess's law, we can write this using enthalpies of combustion of reactants and products: δ H_hydro = δ H_comb(C6H10, l) + δ H_comb(, g) - δ H_comb(C6H12, l) = -3800 + (-241) - (-3920) = -4041 + 3920 = -121 kJ/mol.

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