# How can you find a limiting reactant in a reaction?

Oct 6, 2016

#### Answer:

A stoichiometrically balanced equation is an absolute prerequisite.

#### Explanation:

For many reactions, the reagent in deficiency is obvious. Consider combustion reactions; here, a limited amount of hydrocarbon is combusted in an unlimited quantity of dioxygen gas.

And thus for methane, we write:

$C {H}_{4} \left(g\right) + 2 {O}_{2} \left(g\right) \rightarrow C {O}_{2} \left(g\right) + 2 {H}_{2} O \left(g\right)$

Here, of course, the reagent in deficiency is the hydrocarbon; the oxygen derives from the atmosphere. Under conditions of limited oxygen, and long chain hydrocarbon fuels, for instance in the internal combustion engine, $C O$ and $C$, are observed as oxidation products, and these products represent incomplete combustion.

I presume you know how to convert mass to moles, and vice versa; if not give us a shout, and someone here will help you.