Calculate how much carbon dioxide is formed from 25 g of marble containing 25% impurities.

1. Let’s compose the equation of the chemical reaction:

CaCO3 = CaO + CO2.

2. Find the amount of calcium carbonate:

ω (CaCO3) = 100% – ω (impurities) = 100% – 25% = 75%.

m (CaCO3) = m (mixture) * ω (CaCO3) / 100% = 25 g * 75% / 100% = 18.75 g.

n (CaCO3) = m (CaCO3) / M (CaCO3) = 18.75 g / 100 g / mol = 0.1875 mol.

3. According to the reaction equation, we find the amount, and then the volume of carbon dioxide (Vm – molar volume, constant equal to 22.4 l / mol):

n (CO2) = n (CaCO3) = 0.1875 mol.

V (CO2) = n (CO2) * Vm = 0.1875 mol * 22.4 l / mol = 4.2 l.

Answer: V (CO2) = 4.2 liters.