Practice question
Question
How many grams of O₂ are required to react with 12 g of Mg to form MgO if the reaction proceeds with 75% efficiency? (Atomic masses: Mg = 24, O = 16)
Explanation
Reaction: 2Mg + O₂ → 2MgO. Moles of Mg = 0.5 mol; needs 0.25 mol O₂ (8 g). With 75% efficiency, total O₂ = 8 / 0.75 ≈ 10.67 g.