Answer:
Mass = 182.4 g
Explanation:
Given data:
Number of moles of Al₂O₃ = 3.80 mol
Mass of oxygen required = ?
Solution:
Chemical equation:
4Al + 3O₂   →    2Al₂O₃
Now we will compare the moles of aluminum oxide and oxygen.
        Al₂O₃      :      O₂
          2        :       3
         3.80       :     3/2×3.80 = 5.7
Mass of oxygen:
Mass = number of moles × molar mass
Mass = 5.7 mol × 32 g/mol
Mass = 182.4 g