Answer:
is 4
Explanation:
Fe + 3O₂ → 2Fe₂O₃
The law of conservation of mass states that "matter is neither created or destroyed in a system". Now, by careful inspection of the atoms reacting and the product formed, we see that the equation is not balanced.
Fe on reactant side is 1 but 4 on the product side. To balance it up, we simply put 4 as the coefficient behind the iron atoms.
4Fe + 3O₂ → 2Fe₂O₃
