Question

The amount of calcium oxide produced on heating 150 kg limestone (75% pure) is _______ kg. (Nearest integer)
Given: Molar mass (in g mol$^{-1}$) of Ca-40, O-16, C-12

Hint:

When calculating mass from moles, always use the correct molar masses and conversion factors (grams to kilograms) to ensure accurate results.

Answer 1

Correct Answer: 63

To determine the mass of calcium oxide (CaO) resulting from the heating of 150 kg of limestone (CaCO₃), assuming 75% purity, the following steps are performed:

1. Determine the mass of pure CaCO₃: Given the limestone's purity is 75%, the mass of pure CaCO₃ is calculated as 75% of 150 kg.
Mass of pure CaCO₃ = 0.75 × 150 kg = 112.5 kg.

2. Reference the chemical reaction:
CaCO₃ (s) → CaO (s) + CO₂ (g)

3. Calculate molar masses:
Atomic masses: Ca = 40, C = 12, O = 16.
Molar mass of CaCO₃ = 40 + 12 + (16×3) = 100 g/mol.
Molar mass of CaO = 40 + 16 = 56 g/mol.

4. Convert the mass of CaCO₃ to moles: 
Moles of CaCO₃ = \(\frac{112,500\, \text{g}}{100\, \text{g/mol}}\) = 1125 moles.

5. Convert moles of CaCO₃ to moles of CaO: The balanced chemical equation indicates a 1:1 molar ratio between CaCO₃ and CaO, thus, moles of CaO = 1125 moles.

6. Calculate the mass of CaO: 
Mass of CaO = (moles of CaO) × (molar mass of CaO) = 1125 moles × 56 g/mol = 63000 g = 63 kg.

7. Range verification: The calculated mass of CaO is 63 kg, which is consistent with the specified range of 63-63 kg.

Consequently, the quantity of calcium oxide produced is 63 kg.