Question

From 200 mg of Co2 , 10^21 molecules are removed. How many molecules of carbon dioxide are left ?

Answer 1

Total mass of carbon dioxide which is Given to us = 200 mg

And we know that the molar mass of CO2 = 44 g/mol

1 molecule = 6.022 × 10^23

In this way we can find out the mass of 10^21 molecules.

That is = 73.1 mg

Then after finding the left CO2 we can find the moles left .

For full solution refer to the above attachment !!

Answer 2

Molar Mass of CO2 = 44 g

6.022 × 10^23 molecules of CO2 = 44 g

10^21 molecules of CO2 = (44×10^21)/(6.022×10^23) g = 73.1 mg

CO2 left = 200-73.1 = 126.9 × 10^-3 g

Moles left = (12.9×10^-3)/44 = 2.88 × 10^-3