Mass fraction of impurities in limestone is 5%. Calculate the mass of the basic substance

Mass fraction of impurities in limestone is 5%. Calculate the mass of the basic substance (calcium carbonate) contained in 400 kg of natural limestone.

Given:
ω (impurities) = 5%
m (limestone) = 400 kg
To find:
m (CaCO3) -?
1) Calculate the mass fraction of calcium carbonate in limestone:
ω (CaCO3) = 100% – ω (impurities) = 100% – 5% = 95%;
2) Calculate the mass of calcium carbonate:
m (CaCO3) = ω (CaCO3) * m (limestone) / 100% = 95% * 400/100% = 380 kg.
Answer: The mass of calcium carbonate is 380 kg.