The right option for the mass of CO₂ produced by heating 20 g of 20% pure limestone is (Atomic mass

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Question

The right option for the mass of CO₂ produced by heating 20 g of 20% pure limestone is (Atomic mass of Ca = 40)
CaCO₃ → CaO + CO₂

Accepted Answer

Correct Answer: B — 1.76 gStep-by-step Solution:Step 1 — Find mass of pure CaCO₃: The sample of limestone is 20 g and is 20% pure (i.e., 20% of it is CaCO₃, rest is impurities).Mass of pure CaCO₃ = 20 g × (20/100) = 20 × 0.20 = 4 gStep 2 — Calculate moles of CaCO₃: Molar mass of CaCO₃ = 40 + 12 + 3(16) = 40 + 12 + 48 = 100 g/mol. Moles of CaCO₃ = 4/100 = 0.04 molStep 3 — Use stoichiometry: From the balanced equation: CaCO₃ → CaO + CO₂. 1 mol CaCO₃ → 1 mol CO₂. Therefore, 0.04 mol CaCO₃ → 0.04 mol CO₂.Step 4 — Calculate mass of CO₂: Molar mass of CO₂ = 12 + 2(16) = 44 g/mol. Mass of CO₂ = 0.04 × 44 = 1.76 gWhy other options are wrong:Option A (1.12 g): This would come from 0.04 × 28 = 1.12 — using M(CO) = 28 instead of M(CO₂) = 44.Option C (2.64 g): This would come from using 30% purity instead of 20%, or incorrect molar mass.Option D (1.32 g): Likely an arithmetic error.Key Concepts:% purity: Mass of pure substance = (% purity/100) × mass of sample.Mole concept: Moles = Mass/Molar mass.Stoichiometry: Ratio of moles from balanced equation relates reactants and products (here 1:1 for CaCO₃:CO₂).Molar mass: CaCO₃ = 100 g/mol; CaO = 56 g/mol; CO₂ = 44 g/mol.Limestone (CaCO₃) is used in cement production; its thermal decomposition is called calcination.

The right option for the mass of CO₂ produced by heating 20 g of 20% pure limestone is (Atomic mass of Ca = 40) CaCO₃ → CaO + CO₂

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The right option for the mass of CO₂ produced by heating 20 g of 20% pure limestone is (Atomic mass of Ca = 40) CaCO₃ → CaO + CO₂

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