Question

The enthalpy of combustion at 25 c of h2 , cyclohexane and cyclohexene are 241, 3920 and 1 3800kj mole respectively. The heat of hydrogenation of cyclohexene is

Answer 1

Answer:

Heat of hydrogenation of cyclohexene (C₆H₁₀)

ΔH= -10121 kJ

Explanation:

Given

Enthalpy of combustion of h2 = 241 kJ/ mol

Enthalpy of combustion of cyclohexane (C₆H₁₂) = 3920 kJ/ mol

Enthalpy of combustion of cyclohexene (C₆H₁₀) = 13800 kJ/ mol

Heat of hydrogenation of cyclohexene = ??

Solution

From the given data, we can write:

H₂ + 12 O₂ ----------> H₂O       (1)                               ΔH= −241kJ

C₆H₁₂ + 9 O₂ ----------> 6 CO₂ + 6 H₂O      (2)          ΔH= −3920kJ

C₆H₁₀ + 172 O₂ ----------> 6 CO₂ + 5 H₂O    (3)        ΔH= −13800kJ

Hydrogenation reaction of cyclohexene can be written as

C₆H₁₀ + H₂ ----------> C₆H₁₂

By adding equation (1), (2) and (3), we get

ΔH= −241 + (− 13800) − (−3920)

ΔH= -10121 kJ