The enthalpy of combustion of `H_(2)` , cyclohexene `(C_(6)H_(10))` and cyclohexane `(C_(6)H_(12))` are `-241` , `-3800` and `-3920KJ` per mol respectively. Heat of hydrogenation of cyclohexene is

Options

A. `-121 kJ mol^(-1)`
B. `+121 kJ mol^(-1)`
C. `-242 kJ mol^(-1)`
D. `+242 kJ mol^(-1)`

Answer

A

Explanation

`C_(6)H_(12)+9O_(2)to6CO_(2)+6H_(2)O`, `DeltaH_(1)= -3920 kJ`
`C_(6)H_(10)+(17)/(2)O_(2)to6CO_(2)+5H_(2)O`, `DeltaH_(2)=-3800 kJ`
`H_(2)+(1)\(2)O_(2)toH_(2)O`, `DeltaH_(3)=-241 kJ`
Now operate as
`(DeltaH_(2)+DeltaH_(3)-DeltaH_(1))` will give the value of `DeltaH` for the reaction
`C_(6)H_(10)+H_(2)toC_(6)H_(12)`, `DeltaH=-121 kJ mol`