We decompose 400 g of calcium carbonate which contains 10% impurities. How many grams of calcium iron oxide will you make?

1) Find the mass of impurities in calcium carbonate:
400 – 100%
x – 10%.
x = 400 * 10: 100 = 40 (g).
2) Calculate the mass of pure calcium carbonate by the formula:
Mass of CaCO3 = mass of CaCO3 with impurities – mass of impurities = 400 – 40 = 360 (g).
3) Let’s write the reaction equation and find the mass of the obtained calcium oxide:
CaCO3 -> CaO + CO2.
x = 360 * 56: 100 = 201.6 (g).
As you can see, as a result of this reaction, calcium oxide is formed, weighing 201.6 (g). Iron oxide cannot form here, since the chemical element Fe (iron) is not included in calcium carbonate (CaCO3).