Calculate the number of molecules left when `10^(21)` molecules of `CO_(2)` are removed from 200 mg of `CO_(2)`.

Explanation

200 mg of `CO_(2)=0.2` g of `CO_(2)` (gram-molecular mass of `CO_(2)=44g).44g" "CO_(2)` contains `6.022xx10^(23)` molecules.
`therefore 0.2g" "CO_(2)` contains=`(6.022xx10^(23)xx0.2)/(44)` molecules
`=2.7372xx10^(21)` molecules
On removing `10^(21)` molecules, number of `CO_(2)` molecules
remaining`=2.7372xx10^(21)-1x10^(21)=1.7372xx10^(21)`.