which of the following chemical equations is balanced?
O Fe₂O₃+ CO → Fe + 2CO₂
O Na₂SO₂+ S → S₂O₃ + S
O 3CuO + 2NH₃ → 3Cu + 3H₂O + N₂
O 4Al + 3Fe₃O₄ → 4Al₂O₃+ 9Fe