Question

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

• A. 1.76 g
• B. 2.64 g
• C. 1.32 g
• D. 1.12 g

Answer 1

The Correct Option is A

To calculate the mass of \(CO_2\) produced by heating 20 g of 20% pure limestone, we need to follow these steps:

1. Calculate the mass of pure \(CaCO_3\) in the limestone:
   • The limestone is 20% pure, so the mass of pure \(CaCO_3\) is: \(\frac{20}{100} \times 20 = 4 \text{ g}\)
2. Write down the decomposition reaction of \(CaCO_3\):
   • The reaction is: \(\text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2\)
3. Calculate the molar masses:
   • \(\text{Molar mass of CaCO}_3 = 40 + 12 + 3 \times 16 = 100 \text{ g/mol}\)
   • \(\text{Molar mass of CO}_2 = 12 + 2 \times 16 = 44 \text{ g/mol}\)
4. Use stoichiometry to find the mass of \(CO_2\) produced:
   • The equation shows that 100 g of \(\text{CaCO}_3\) produces 44 g of \(\text{CO}_2\).
   • Therefore, 4 g of \(\text{CaCO}_3\) will produce: 
     \(\frac{44}{100} \times 4 = 1.76 \text{ g of CO}_2\)

Therefore, the mass of \(\text{CO}_2\) produced is 1.76 g.