`DeltaH` combustion for `CH_(4),C_(2)H_(6)`, and `C_(3)H_(8)` are `-210.8,-368.4` and `-526.3 kcal mol^(-1)`, respectively. Calculate `DeltaH` combustion for octane.

Explanation

The difference in `DeltaH` combustion between `CH_(4)` and `C_(2)H_(6)` is `-157.6 kcal` and between `C_(2)H_(6)` and `C_(2)H_(8)` is
`- 157.6 kcal (~~ -15.75 "average")`
i.e., `Delta_(comb)H of CH_(2) =- 157.75`
`Delta_(comb)H(C_(8)H_(18)) = Delta_(comb)H (C_(3)H_(8)) +5 Delta_(comb)H(CH_(2))`
`=- 526.3 +5 +(-157.75)`
`=- 1315.5 kcal`