How much gas forms when 50 g of CaCO₃ is heated?

Correct answer: d 22 g

CaCO₃ -Δ→ CaO + CO₂: 100 g gives 44 g of CO₂, so 50 g gives 22 g.

Why the other options are wrong

• a 56 g: 56 g is the CaO from 100 g of CaCO₃, not a gas; the answer is 22 g.
• b 44 g: 44 g of CO₂ comes from a full 100 g of CaCO₃; 50 g gives half, 22 g.
• c 28 g: 28 g is the CaO from 50 g of CaCO₃, a solid, not the gas; the gas CO₂ is 22 g.