From the following data, calculate the enthalpy change for the combustion of cyclopropane at `298K`. The enthalpy of formation of `CO_(2(g)),H_(2)O_((l))` and `Propen e_((g))` are `-393,-285.8` and ` 20.42 kJ mol^(-1)` respectively. The enthalpy of isomerisation of cyclopropane to propene is `-33.0kJ mol^(-1)`

Explanation

For the reaction,
i. `CH_(3)CH =CH_(2)(g) +9//2O_(2)(g) rarr 3CO_(2) +3H_(2)O(l) ..(i)`
`Delta_(r)H =3Delta_(f)H (CO_(2),g) +3Delta_(f)H(H_(2)O,l) -Delta_(f)H (CH_(3)-CH =CH_(2))`
`[3(-393.5)+3(-285.8) -(20.42)] kJ mol^(-1)`
`=- 2058.32 kJ mol^(-1)`
To reaction (i), if we add the reaction

`Delta_(r)H =- 33.0 kJ mol^(-1)`
We get

`Delta_(comb)H_(("cyclopropene")) = (-2058.32 -33.0) kJ mol^(-1)`
`=- 2091.32 kJ mol^(-1)`