Question: how many molecules are in 1.0 l of o2 at stp?
Answer: Therefore this volume contains 134.522.4=6mol . But 1 mole contains an Avagadro number of particles, ie 6.023×1023 . Therefore by ration and proportion, 6 moles of oxygen will contain 6×6.023×1023=3.6138×1024 oxygen molecules.