WAEC Chemistry 2018 Theory — Question 3
Question 3 of 24 from the West African Examinations Council (WAEC) Chemistry 2018 Theory paper, with the correct answer and a full explanation.
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1.(c) Consider the reaction: Fe + H₂SO₄ → FeSO₄ + H₂. Calculate the mass of unreacted iron when 5.0g of iron reacts with 10cm³ of 1.0moldm⁻³ H₂SO₄ [Fe=56.0]
Model answer
n(H₂SO₄) = 1moldm⁻³ × (10/1000)dm³ = 0.01mol. Since the mole ratio Fe:H₂SO₄ is 1:1, mol Fe reacted = 0.01mol. Mass Fe reacted = 0.01×56 = 0.56g. Mass of unreacted Fe = 5.0 − 0.56 = 4.44g.
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