What mass of CaO, can get by the decomposition of 250 g of CaCo3 with 80% purity?

Answer 1

CaCO3 ==> CaO + CO2
grams CaCO3 = 250 x 0.8 = 200g.
mols CaCO3 = 200/molar mass CaCO3

Using the coefficients in the balanced equation, convert mols CaCO3 5o mols CaO.

Now convert mols CaO to g. g CaO = mols CaO x molar mass CaO.