Question: how many molecules are in 2.0 moles of molecular hydrogen?
Answer: For example, since one atom of oxygen will combine with two atoms of hydrogen to create one molecule of water (H2O), one mole of oxygen (6.022 × 1023 of O atoms) will combine with two moles of hydrogen (2 × 6.022 × 1023 of H atoms) to make one mole of H2O.