How many atoms of oxygen are present in 50 g of calcium carbonate?
The chemical formula of calcium carbonate is CaCO3 and its molar mass is 100g. This means there are 6.022 X 1023 units of CaCO3 in 100g of CaCO3. Thus
number of units of CaCO3 in 100g of CaCO3 = 6.022 X 1023
number of units of CaCO3 in 1g of CaCO3 = (6.022 X 1023) / 100
number of units of CaCO3 in 50g of CaCO3 = (6.022 X 1023 X 50) / 100
= 3.011 X 1023
Thus there are 3.011 X 1023 units of CaCO3 in 50g of the compound. Now, each unit of CaCO3 contains 3 oxygen atoms. So
number of oxygen atoms in one unit of CaCO3 = 3
number of oxygen atoms in 3.011 X 1023 units of CaCO3 = 3 X 3.011 X 1023
= 9.033 X 1023
Hence there are 9.033 X 1023 atoms of oxygen in 50g of CaCO3.