One liter of water has a mass of 1000 grams. Molar mass of water is 18.016 g/mol. One liter of water contains 55.5 moles of water molecules (55.5 moles of hydrogen and 27.75 moles of oxygen). Avogadro's rule for molar volume states that one mole of any ideal gas occupies 22.4 liters of volume.read more >>