My daughter stump me on a question related to liters and grams in stoichiometry. Wondering if someone could help explain. First we know that 1 mole always eqauls 22.4 liters at STP. And 1 mole also always equals the selected element's atomic mass in grams on the periodic table. So... Let's say you're dealing with Oxygen which has an atomic mass of 16 grams. Therefore: 1 mole of O is 16g 1 mole of O2 is 32g 1 mole of O3 is 48g You multiple the periodic table atomic mass be the number of atoms you have in the given molecule. Here's the question: Why don't you do that on the liters side too? Why isn't: 1 mole of O = 22.4 L 1 mole of O2 = 44.8LL 1 mole of O2 = 67.2L If you have more mass wouldn't you have more volume?