Home › MCQs › MDCAT Chemistry › Question #7788
Back to Questions
MDCAT Chemistry QUESTION #7788
Question 1

What mass of \(\mathrm{Al}_2\mathrm{O}_3\) is produced from 18.5 g Al? \(4\mathrm{Al} + 3\mathrm{O}_2 \rightarrow 2\mathrm{Al}_2\mathrm{O}_3\)

  • 30.8 g
  • 32.6 g
  • 34.9 g✔️
  • 36.5 g
Correct Answer Explanation

Molar mass Al = 27 g/mol: moles Al = 18.5/27 = 0.685 mol. From stoichiometry: 4 mol Al → 2 mol Al₂O₃, so mol Al₂O₃ = 0.685/2 = 0.3425 mol. Molar mass Al₂O₃ = 102 g/mol: mass = 0.3425×102 = 34.94 g ≈ 34.9 g.