 Okay, so how many moles of oxygen are in 12.23 grams of water? Okay, so on the surface, this might seem like a very difficult problem, okay? But in actuality, it's only a couple of steps that you need to know, okay? So if you look at the periodic table, that will tell you most of the information that you need to know for this problem. The first thing I would do is figure out the molecular weight of water, okay? So how do I do that? Molecular weight of water, okay? Well, we remember how to calculate the molecular weight, hopefully, right? We add two hydrogens because there's two hydrogens of water. So two times the atomic weight of hydrogen. So H, two times H plus one oxygen there, one times O. The periodic table will know that hydrogen plays 1.008 AMU. Oxygen, of course, multiplying one times anything is itself, so we don't have to put that one there. Oxygen is 16.00 AMU. If we add those two numbers together, we get 18.02 AMU. I just did that in my head, but I would suggest you guys do it on your calculator just to make sure that you know what's going on, and I got the right answer. Okay, so we would do the two times 1.008 AMU. So what is... I mean, you guys can talk, we can talk, but I mean, we can talk about it afterwards. That's 12.23 grams in here, is that... Wait, that's not this cool, and the question isn't finished yet. Oh. This is fit... I figured out something totally different than what I'm saying. This doesn't say anything about moles. All right. Okay, so let's just finish the problems, and then we can ask as many questions as you want, okay? I mean, but if not, we can talk as much as we want to. Everybody else is seriously too, forever, you know? Think about that. Okay, so now we've got this 18.02 AMU, right? The thing we know is the amount of AMUs is going to be equivalent to the molecular weight of the... or the molar mass of the contact. So the molar mass of water is going to be equivalent, but it's going to have different units. The units are going to be grams per mole. So we're going to have 18.02 grams per one mole. Like that. That's the molar mass. So now we'll figure out what this 12.23 grams had to do with anything. So the next thing we've got to do is figure out how many moles of water we've got. How do we figure out that? So the variable for water or moles is N. Okay, so I'll just put N of water. N means moles of water, do we have? 12.23. And we've got a conversion factor that takes grams to moles, right? We're going to get the number of moles of water. 23 divided by 18. I got 0.6787 whatever moles. 0.6787 whatever. In fact, I could take this even to more stig figs for right now. Let's do that, 6.98 for right now. Because this isn't the final answer, right? This is where we have moles of water. And we don't want that. We want moles of oxygen, right? So how many moles of oxygen are there for moles of water? So how many oxygens are there in each water mole? One. One. So for every one mole of water, there's how many moles of oxygen? One, okay? It's a one to one ratio, right? One mole of water equals one mole of oxygen. Just like for every heat, there's one head. If I had two heats, how many heads would I have? Two heads. So now all we've got to do is take this to figure out the number of moles of oxygen. And in fact, it's going to be the same number. But we've got to get our units out. Multiply that by our new conversion factor. One mole of water, mole of water cancels out. And we've got mole of oxygen. So it's going to be 0.67. And we've got to take it to four significant figures. 6, 7, 8, 7 moles of oxygen, okay? So you could write it like that. That would be fine. Or you could put it into scientific notation, which would be 6.787 times 10 to the negative one. Okay, so I mean, you don't need to use Apogadro's number, but we can. Let's do this problem again using Apogadro's number, okay? Like everybody always wants to do. Makes it so hard on us. I don't want to do it.