The polymerisation of propene to linear polypropene is represented by the reaction
where `n` has intergral value, the average enthalpies of bond dissociation for `(C =C)` and `(C -C)` at `298K` are `+509` and `+331 kJ mol^(-1)`, respectively. the enthalpy of polymerisation is `-360 kJ`. Find the value of `n`.

Explanation

Energy released = Energy due to formation of two single bonds
`= 2xx 331 = 662 kJ mol^(-1)` of propene
`DeltaH` polymerisation/mol `=590 - 662 =- 72 kJ mol^(-1)`
`DetaH` polymerisation `=- 72 xx n =- 360`
`n = 5`