First, lets balance the reaction equation:
4Fe + 3O₂ → 2Fe₂O₃
It is visible form the equation that 4 moles of Fe require 3 moles of Oâ‚‚
Molar ratio Fe/Oâ‚‚ = 4/3 = 1.33
Molar ratio Oâ‚‚/Fe = 3/4 = 0.75
Now, we check the molar ratios present:
Fe/Oâ‚‚ = 6.8/8.9 = 0.76
Oâ‚‚/Fe = 1.31
Thus, Iron is the limiting reactant because its ratio is not being fulfilled while the ratio of Oâ‚‚ is surpassed.