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

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