Calcium carbonate, CaCO3, when heated decomposes to calcium oxide and carbon dioxide. Calulate the mass of clacium oxide formed when 2.0 grams of CaCO3 is decomposed.

Answer 1

CaCO3 ==> CaO + CO2
mols CaCO3 = grams/molar mass = ?

Using the coefficients in the balanced equation, convert mols CaCO3 to mols CaO. That's 1:1 so mols CaCO3 = mols CaO.
Then g CaO = mols CaO x molar mass CaO.