Question

The standard enthalpy of combustion at 25ºC of hydrogen, cyclohexene (C₆H₁₀) and cyclohexane (C₆H₁₂) are –241, –3800 and –3920 kJ/mole respectively. Calculate the heat of hydrogenation of cyclohexene.

Answer 1

Answer: -121 kJ/mol

C6H12+9O2→6CO2+6H2OC6H12+9O2→6CO2+6H2O ; ΔH1=−3920ΔH1=−3920 kJ/mol

C6H10+172O@→6CO2+5H2OC6H10+172O@→6CO2+5H2O ; ΔH2=−3800ΔH2=−3800 kJ/mol

H2+12O2→H2OH2+12O2→H2O ; ΔH3=−241ΔH3=−241 kJ/mol

Now operate as, (ΔH2+ΔH3−ΔH1ΔH2+ΔH3−ΔH1) will give the value of ΔHΔH for the reaction

C6H10+H2→C6H12C6H10+H2→C6H12 ; ΔH=−121ΔH=−121 kJ/mol