When 3 moles of iron react with 2 moles of oxygen gas to form iron(III) oxide, which reactant acts as the limiting reagent?
Correct answer: B. O₂
- A. Fe
- B. O₂
- C. Both react completely
- D. None
Explanation
Balanced equation: 4Fe + 3O₂ → 2Fe₂O₃. For 2 mol O₂, 2.67 mol Fe are required; 3 mol Fe are present, so Fe is slightly in excess. However, per stoichiometry, oxygen limits the reaction, as it will be used up first. So, O₂ is limiting one.
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Mole calculations connect mass, number of particles and Avogadro's number, while balanced equations provide the mole ratios used in stoichiometry. Questions cover limiting and excess reactants, theoretical yield and percentage yield, including identifying which reactant is consumed first and comparing the actual product with the maximum possible product.
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