=> The molar mass of Calcium Carbonate is 100 g/mole,

We have 200 g, therefore, we have 2 moles,

the number of molecule per mole is 6.02 x 10^{23},

**Therefore we have 1.204 x 10**^{24} molecules.

=> Molecular mass of CaCO3 = 40 + 12 + (3 x 16) = 100 g [Molecular weight of Ca = 40, C = 12, O =16]

1 mole of Oxygen atoms = 6.022 x 10^{23} Oxygen atoms (Avogadro’s number)

1 mole of Calcium Carbonate = 100 g of Calcium Carbonate

100 g of Calcium Carbonate has 3 moles of Oxygen atoms = 3 x 6.022 x 10^{23} Oxygen atoms.

**So, 200 g of Calcium Carbonate has 6 moles of Oxygen atoms = 6 x 6.022 x 10**^{23} Oxygen atoms.