Chemical reaction: 3Fe + 4H₂O → Fe₃O₄ + 4H₂<span>. From chemical reaction: 1) n(Fe) : n(H</span>₂) = 3 : 4. Four molecules of hydrogen are produced. 2) n(Fe) : n(H₂O) = 3 : 4. Four molecules of water are required, because the mole ratio of Fe to H₂O is 3:4. 3) Hydrogen molecules are not<span> involved in this reaction, but produced (4 molecules).</span>