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

`H_(2)(g)+(1)/(2)O_(2)(g) rarr H_(2)O(l) (Delta H = -241 kJ)` ...(i)
`C_(6)H_(10) +(17)/(2)O_(2)(g) rarr 6CO_(2)(g)+5H_(2)O(l)`
`(Delta H = -3800 kJ)` ...(ii)
`C_(6)H_(12)+9O_(2)(g) rarr 6CO_(2)(g)+6H_(2)O(l)`
`Delta H = -3920 kJ)` ...(iii)
Eq. (i) + eq. (ii) -eq. (iii) gives
`Delta H = -241-3800-(-3920) = -121 kJ`
for `C_(6)H_(10) + H_(2) rarr C_(6)H_(12)`