Answer:
Fe₂O₃ + 3H₂ ⟶ 2Fe + 3H₂O
Explanation:
Fe₂O₃ + H₂ ⟶ Fe + H₂O
We could balance this equation by inspection, but I will choose the oxidation number method.
1. Calculate the oxidation number of every atom:
Fe₂⁺³O₃⁻² + H₂⁰ ⟶ Fe⁰ + H₂⁺O²⁻
2. Identify the changes in oxidation number:
Fe: +3 ⟶ 0; Change = -3
H: 0 ⟶ +1; Change = +1
3. Equalize the changes in oxidation number.
You need 3 atoms of H for every 1 atom of Fe or 6 atoms of H for every 2 atoms of Fe. This gives us total changes of +6 and -6.
4. Insert coefficients to get these numbers.
1Fe₂O₃ + 3H₂ ⟶ 2Fe + 3H₂O
Every formula has a coefficient. The equation should be balanced.
5. Check that all atoms balance.
Atom Left-hand side Right-hand side
Fe 2 2
O 3 3
H 6 6
OK.
The balanced equation is
Fe₂O₃ + 3H₂ ⟶ 2Fe + 3H₂O
