 Okay, guys, so let's try another one of these Grams' Laws of Fusion problems. So this one in particular says, what is the rate of effusion of oxygen molecules if we have a mixture of oxygen and helium? And the rate of helium effusion is 2.76 x 10 to the negative fourth moles per second. So in order to do this problem, we have to recall Grams' Law of Effusion, okay? So does anybody remember that? Can you guys help me with that one? So, yeah, rate 1 divided by rate 2, yeah, very good. That equals what? Square root of smaller mass of 2 divided by smaller mass of 1, okay? So remember that, Law, if you don't remember that equation, you can't do these problems. Okay? So, well, what does that mean? Well, then that means we need to figure out what the molar mass of these things is, okay? So what did it say, it was molar mass of helium and the molar mass of oxygen. So oxygen, we have to remember, is the diatomic molecule. So if we forget that, and we put just 16 from the periodic table, we're not going to get the correct answer, okay? So oxygen's diatomic, so it's going to be 2 times 16. We get that number from the periodic table, 32.00 molar mass grams per mole. And helium, of course, we look at the periodic table, 4.002, okay? So let's plug that into this equation. Well, it doesn't say helium and an oxygen, so let's rewrite this equation to include those. So we're looking for the rate of oxygen, so why don't we just put it here so we can have that variable be easily isolated, okay? So I'm going to put a set of 1, I'll put O2 there, and O2 there, and here, and here, and here, and here, okay? The other thing I like to do, I don't really like to work with this square root symbol. I like to put exponents. So if you guys recall, this is the same thing to the one half as the square root, okay? So let's rearrange this to isolate the rate of oxygen here. So what are we going to do? Multiply both sides times the rate of helium. So when we do that, we erase that there, and then multiply this. Okay, wonderful. So can everybody get to this point? Everybody's up here with that, okay? So let's just plug in our numbers. So do we have all this? Yes, rate of helium, molar mass of helium, molar mass of oxygen. So we have everything we need. So just a plug-and-check problem. So molar mass of helium, 4.002 grams per mole, and the molar mass of oxygen, 32.00 grams per mole. Okay? So the one half times the rate of helium, which is going to be 2.76 times 10, so it's going to be negative 4 moles per second, okay? So when we do that, hopefully you see grams per mole, cancels with grams per mole there. And our units, our final units here are going to be in moles per second, okay? So let's 4.02 divided by 32 to the one half, 2.76. Okay? And I get a number, so the three significant figures, 9.76 times 10. The negative 5th moles per second. So that would be the rate of the fusion of oxygen molecules in this particular set, okay? In this particular system. Is there any questions about this one? Okay, wonderful. We'll do one more of these grams law problems, okay?