Question

How many oxygen atoms are present on the reactant side of the chemical equation `4Fe + 3O_2 -> 2Fe_2O`?

Answer 1

`4Fe(s)+3O_2(g)rarr2Fe_2O_3`

Explanation:

Clearly, there are `6` oxygen atoms on the left hand side of the equation; and, equally clearly, there are `6` oxygen atoms on the right hand side of the equation, as indeed there must be in a stoichiometrically balanced equation.

The oxidation of iron in structures is of special concern; see here.