If 2.0 mol of propane are burned (reacted with oxygen), how many moles of carbon dioxide will be produced?

Propane, C3H8, a fuel used in many outdoor grills, burns in oxygen to produce carbon dioxide gas, CO2, and water vapor, H2O, as shown in the reaction $\text{C"_3"H"_8 (g) + 5"O"_2(g) -> 3"CO"_2(g) + 4"H"_2"O} \left(g\right)$

Jun 9, 2017

${\text{6.0 moles CO}}_{2}$

Explanation:

The thing to remember about balanced chemical equations is that the stoichiometric coefficients added to each chemical species that takes part in the reaction are equivalent to moles.

In your case, you know that the chemical equation that describes the combustion of propane looks like this

${\text{C"_ 3"H"_ (8(g)) + 5"O"_ (2(g)) -> color(red)(3)"CO"_ (2(g)) + 4"H"_ 2"O}}_{\left(g\right)}$

Notice that you don't have a coefficient for propane, which implies that the coefficient is actually equal to $1$, and that you have a $\textcolor{red}{3}$ for carbon dioxide.

This tells you that when $1$ mole of propane undergoes combustion, $\textcolor{red}{3}$ moles of carbon dioxide are produced.

You can thus say that when $2.0$ moles of propane react, you will get

$2.0 \textcolor{red}{\cancel{\textcolor{b l a c k}{{\text{moles C"_3"H"_8))) * (color(red)(3)color(white)(.)"moles CO"_2)/(1color(red)(cancel(color(black)("mole C"_3"H"_8)))) = color(darkgreen)(ul(color(black)("6.0 moles CO}}_{2}}}}$

The answer is rounded to two sig figs.