Ethanol, C₂H₅OH, is used to introduce oxygen into some blends of gasoline. It has a heat of combustion of 1366.8 kJ/mol. What is the heat of formation of ethanol?

Strategy We know the relationship between the heat of combustion of a reaction and the heats of formation of the substances involved. We will need a balanced chemical equation for the combustion, and we must recognize that the combustion of ethanol yields the same products as hydrocarbon combustion. We can write the balanced equation and then use Equation 9.12 to determine the desired quantity.

Equation 9.12

 

In this case, we know the heat of reaction and will be solving for one of the heats of formation.

Transcribed Image Text:

ΔΗ° = ΣυΔΗ;° (product) - ΣυΔΗ,° (reactant);