To find a molecular weight, we simply add up the atomic weight of each atom. So, 23 moles per gram, or grams per mole for sodium, plus 16 grams/mol for oxygen, plus 1 gram/mol for h, and we get 40 grams/mol times the number of moles. Moles cancel, and we get 10 grams of sodium hydroxide mixed into our solution. Our third step is to follow the same exact steps that we just followed just for hydrophoric acid. So find the moles. 1 mol per liter times zero point 25 liters gets you zero point 25 moles of hydrofluoric acid.