2 mol Al and 3 mol O₂ react according to: 4Al + 3O₂ → 2Al₂O₃ Which is the limiting reagent?

4 mol Al require 3 mol O₂. 2 mol Al require only 1.5 mol O₂. Since 3 mol O₂ are available, O₂ is in excess and Al is limiting.