How do we determine the number of moles of carbon dioxide that result from the combustion of a particular fuel?

Sep 7, 2016

How else but write a stoichiometric equation?

Explanation:

Hydrocarbon combustion is an area whose stoichiometry you should master fairly quickly. Complete combustion of a hydrocarbon, say hexane, results in carbon dioxide and water as the products:

${C}_{6} {H}_{14} \left(l\right) + \frac{19}{2} {O}_{2} \left(g\right) \rightarrow 6 C {O}_{2} \left(g\right) + 7 {H}_{2} O \left(l\right) + \Delta$

When you write equations that represent the combustion of OTHER hydrocarbons, say pentane, or methane, or octane, the usual rigmarole is to (i) balance the carbons as carbon dioxide, (ii) balance the hydrogens as water, and then (iii) balance the oxygens.. You should try it out.

Now, (i) this equation is balanced with respect to mass and charge; (ii) the equation is also balanced with respect to energy. A given quantity of hexane will evolve a given quantity of heat upon combustion, i.e. $\Delta {H}^{\circ} \text{_"combustion"" n-hexanes} = - 4180 \cdot k J \cdot m o {l}^{-} 1$.