Hello Student,

1 mole = 6.022*10^23 atoms

So in 10 moles of CO2 the number of oxygen atoms would be

----> 10*6.022*10^23*2 = 1.2044 * 10^25 atoms of oxygen.

Since each CO2 molecules has 2 oxygen atoms therefore 2 is multiplied .

Also if suppose the number of carbon atoms were asked then

answer would be 6.022 * 10^24 .

Hope this helps