How many moles of O2 are there in 1.20 × 1022 oxygen molecules?
Since One mole of O2 contains = 6.022 × 1023 molecules of oxygen
So, 1 molecule of O2 has = 1/6.022 × 1023 moles of O2
Therefore, 1.2 × 1022 molecules of O2 will have = 1.2 × 1022 / 6.022 × 1023 moles of O2
= 0.0199 moles of O2