The equations we have written provide us with a good starting point in our consideration of the chemistry of gasoline or other hydrocarbon fuels. But many of the important questions surrounding the chemistry of fuels are quantitative. How much oxygen is needed to allow complete combustion to occur? How does the amount of CO2 emitted relate to the amount of fuel burned? To begin to answer questions such as these, we will need to consider the stoichiometry of the underlying chemical reactions