How many grams of calcium oxide can be obtained from 400 grams of limestone containing 20 percent impurities?

The limestone roasting reaction is described by the following equation:
CaCO3 = CaO + CO2 ↑;
When decomposing 1 mol of limestone, 1 mol of calcium oxide and 1 mol of carbon monoxide is obtained.
Let’s calculate the molar amount of calcium carbonate. To do this, divide its weight by its molar weight.
M CaCO3 = 40 + 12 + 16 x 3 = 100 grams / mol; N CaCO3 = 400 x 0.8 / 100 = 3.2 mol;
Let’s calculate the mass of 3.2 mol of calcium oxide.
For this purpose, we multiply the amount of the substance by its molar weight.
M CaO = 40 + 16 = 56 grams / mol; m CaO = 3.2 x 56 = 179.2 grams;