Well, an empirical formula can be used to find the percent by mass of any atom in our compound. Now, let's look at this example again. How can we find the percent by mass of hydrogen in our molecule in our compound? Well, what we do is we take our atomic weight of our H, which is 1 gram/mol and divide that by our molecular weight of this guy or the empirical weight of this guy. And what we get is 14 grams/mol. These guys, these units cancel, and we get one over 14, which is 0.7
114.