Initial no. of moles of Al = (5.4 g) / (27 g/mol) = 0.2 mol
Initial no. of moles of O₂ = (9 × 10²² molecules) / (6 × 10²³ molecules/mol) = 0.15 mol
Balanced equation for the reaction :
4Al + 3O₂ → 2Al₂O₃
Mole ratio Al : O₂ : Al₂O₃ = 4 : 3 : 2
If 0.2 mol Al completely reacts, O₂ required = (0.2 mol) × (3/4) = 0.15 mol = Initial no. of moles of O₂
Hence, both Al and O₂ completely react.
No. of moles of Al₂O₃ formed = (0.2 mol) × (2/4) = 0.1 mol
[OR: No. of moles of Al₂O₃ formed = (0.15 mol) × (2/3) = 0.1 mol]
Mass of Al₂O₃ formed = (0.1 mol) × (102 g/mol) = 10.2 g = 10200 mg