 So let's try this problem together. This one says what is the mass in grams of a single chlorine molecule? So remember in order to do this, you're going to have to use that conversion factor that's given to you on the test. 1amu equals 1.661 times 10 to the negative 24th grams. So remember that you got to use that in that. The other thing is that you have to remember that chlorine molecule is diatomic. So it's actually Cl2 like that. So we're wondering what is the mass of a chlorine molecule? So we can look on the periodic table up here, and it says, well the mass of a chlorine atom is 35.45 So what do we have to do? Multiply that right by 2. So 35.45 times 2, how do we get? 70.90. That's not grams remember, that's amu. Okay, so what do we do from here? Just use our conversion factor, right? So use that conversion factor from amu to grams, and so it's just the one step, and then you get your answer. So on the bottom here is 1amu. On the top, 1.661 times 10 to the negative 24th grams. Notice that cancels with that. So we just take 70.90 times 1.661 And we get, since I did four six-fix here, we'll do four six-fix here, 1.178 times 10 to the negative 22 So that's how much one chlorine molecule weighs in grams. Okay, so I expect you guys will be able to know how to do those types of problems from now on. Any questions on this one?