Question

the number of oxygen atoms present in 50g of calcium carbonate is

Answer 1

1 mole of caco3 has 3 moles of oxygen atoms
100 g of caco3 has 3 ×6.022×10^23 atoms
50g of caco3 has 3 ×6.022×10^23/100 ×50
it has 1.5 × 6.022 ×10^23
= 9.033 ×10^23 atoms

Answer 2

NO. OF MOLES OF CaCO3=50/100=0.5 moles
No. Of molecules in 0.5 moles of CaCO3 is 0.5×6.023×10²³=3.0115×
10²³.
One molecule of CaCO3 contain 3 O2 molecules
Then 3.0115×10²³ molecules contain 3.0115×10²³ ×3=
9.0345 ×10²³ molecules