In this video you will practice writing empirical formulas for many molecular formulas. In order to write the empirical formula, you find the largest number you can divide all of the subscripts by, to reduce it as much as possible. You know that you have the empirical formula when your new compound formula cannot be reduced any more. For some formulas, the molecular formula is that same as the empirical formula. Also, it's possible for more than one compound to have the same empirical formula. [6:08]