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MDCAT Chemistry QUESTION #7792
Question 1

4 g of Mg heated in excess O₂. Theoretical yield of MgO (g) is: \(2\mathrm{Mg} + \mathrm{O}_2 \rightarrow 2\mathrm{MgO}\)

  • 3.7 g
  • 4.2 g
  • 5.4 g✔️
  • 6.6 g
Correct Answer Explanation

Molar mass Mg = 24 g/mol: moles Mg = 4/24 = 0.1667 mol. 2 mol Mg → 2 mol MgO, so mol MgO = 0.1667 mol. Molar mass MgO = 40 g/mol: mass = 0.1667×40 = 6.67 g ≈ 6.6 g.