Question: how many molecules of oxygen are present in 8g of oxygen gas?
Answer: 1 g contains → 6.022 × 1023 / 32 molecules of di oxygen. ⇒ 1 g contains → 0.188 × 1023 molecules of di oxygen. ∴ 8 g contains → 0.188 × 8 × 1023 molecules of di oxygen. =1.505 * 1023 molecules.