For the reaction "C"(s) + "O"_2(g) -> "CO"(g)C(s)+O2(g)CO(g), how many mols of "O"_2O2 would be made from "2.04 mols"2.04 mols of "C"C?

1 Answer
Dec 19, 2016

"1.02 mol O"_2(g)1.02 mol O2(g)


Pure carbon in charcoal can simply be considered "C"("s")C(s) (soot). Including the phases, we would have:

"C"("s") + "O"_2(g) -> "CO"(g)C(s)+O2(g)CO(g)

Note that "O"_2O2 exists in nature as a diatomic gas (two identical oxygen atoms bound together).

Carbon monoxide is a covalent compound, so the "mono" is the prefix that indicates that one oxygen is bound to the carbon in this molecule.

As-is, this reaction is unbalanced. Try to keep a tab on the number of atoms on both sides of the reaction; since there are two oxygen atoms on the left, we need two on the right.

It makes physical sense not to add new subscripts, but to double the number of "CO"CO molecules, so that we maintain the structure of the compounds and elements in the reaction:

=> "C"("s") + "O"_2(g) -> color(red)(2)"CO"(g)C(s)+O2(g)2CO(g)

If you notice, we've balanced the oxygens and unbalanced the carbons. So, double the number of carbon atoms on the reactants side to get:

=> color(blue)(color(red)(2)"C"("s") + "O"_2(g) -> color(red)(2)"CO"(g))2C(s)+O2(g)2CO(g)

Since in the actual reaction in the scenario, we have "2.04 mols"2.04 mols of "C"("s")C(s), we should expect to have a little over "1.00 mol"1.00 mol of "O"_2(g)O2(g) reacting.

The actual math gives:

2.04 cancel("mols C"("s")) xx ("1 mol O"_2(g))/(2 cancel("mols C"("s")))

= color(blue)("1.02 mols O"_2(g))

Indeed, a little over "1.00 mol" of "O"_2(g).