Calculate the mass of quicklime CaO which can be obtained by firing 100 kg of limestone containing 10% primis.

The reaction of obtaining quicklime:

CaCO3 = CaO + CO2.

Let’s calculate the mass of pure carbonate taking into account impurities:

m (CaCO3) = m (CaCO3) tech. • W (CaCO3) pure.

Mass fraction without impurities:

W (CaCO3) pure. = 100% – W (CaCO3) tech. = 100% – 10% = 90%

m (CaCO3) = 100 kg • 0.90 = 90 kg

The number of moles of substances will be equal, according to the reaction equation.
n (CaCO3) = m (CaCO3) / M (CaCO3) = 90 kg / 100 kg / kmol = 0.9 kmol.
n (CaO) = n (CaCO3) = 0.9 kmol.

So the mass of the obtained calcium oxide is equal to.
m (CaO) = n (CaO) • M (CaO) = 0.9 kmol • 56 kg / kmol = 50.4 kg.