Question

How do I assess the enthalpy of a combustion reaction, when MORE than one mole of hydrocarbon is combusted?

Answer 1

Enthalpy change, `DeltaH`, is quoted `"per mole of reaction as written."`

Explanation:

For simple hydrocarbon combustions, e.g.

`CH_4(g) + 2O_2(g) rarr CO_2(g) +2H_2O(g)`, `DeltaH=??`

the enthalpy change is quoted per mole of reaction as written. Clearly, if we double the amount of methane combusted we double the energy output of the reaction.