How many atoms of oxygen are present in 50 g of calcium carbonate?

The chemical formula of calcium carbonate is CaCO_{3} and its molar mass is 100g. This means there are 6.022 X 10^{23} units of CaCO_{3} in 100g of CaCO_{3}. Thus

number of units of CaCO_{3} in 100g of CaCO_{3} = 6.022 X 10^{23}

number of units of CaCO_{3} in 1g of CaCO_{3} = (6.022 X 10^{23}) / 100

number of units of CaCO_{3} in 50g of CaCO_{3} = (6.022 X 10^{23} X 50) / 100

= 3.011 X 10^{23}

Thus there are 3.011 X 10^{23} units of CaCO_{3} in 50g of the compound. Now, each unit of CaCO_{3} contains 3 oxygen atoms. So

number of oxygen atoms in one unit of CaCO_{3} = 3

number of oxygen atoms in 3.011 X 10^{23} units of CaCO_{3} = 3 X 3.011 X 10^{23}

= 9.033 X 10^{23}

Hence there are 9.033 X 10^{23} atoms of oxygen in 50g of CaCO_{3}.

**
**