 Okay, here's a little bit more of a drill, again, a refresher. One mole is 6.02 times 10 to the 23 things. I have a mole of hydrogen molecules. If you notice on the previous video, everything I talked about was hydrogen atoms. This time, one molecule is H2, which means two hydrogen atoms stuck to each other. This egg thing that I'm circling is one H2 molecule. So I have a mole of hydrogen molecules. How many hydrogen molecules do I have? Well, I have a mole of them. One mole of hydrogen molecules, how many H2 molecules? I must have 6.02 times 10 to the 23 H2 molecules. Next question. How many hydrogen atoms do I have in my one mole of H2 molecules? So this may be difficult, or this may be a little confusing, because the first question I asked was how many H2 molecules do I have? This time I'm saying, look, how many hydrogen atoms do I have in my one mole of H2 molecules? The answer to that is 2 times 6.02 times 10 to the 23 H atoms. The reason for that is because every one molecule, every, let me erase and show you this nice one here. Every one molecule, this is one molecule of H2, has two H2 hydrogen atoms in it. So think of this as like an egg. If you crack the egg open, there's two H's inside of every one. I told you you have one mole of these little eggs. So you have 6.02 times 10 to the 23 of them. These eggs are called H2 molecules. However, if you crack them open, I want to know how many H's are inside all of them. Well, there's two inside of every one, so I have to have 2 times as much as the number of molecules that I have. Or if you want to keep going with my analogy, I have to have 2 times as much as the number of eggs that I have. And this, again, if you multiply this out, it's going to be about 1.204 times 10 to the 24 H atoms. So the answer to the second question is what I'm circling here. Because for every one molecule, I have two H's as part of the molecule. This question is very similar to the dozen Toyota Corollas and wheels question that I asked in a previous video. In a previous video I said you have one dozen Corollas, how many wheels? And probably nobody had a problem with this. We said, well, a dozen is 12 cars, four wheels per car, that's 48 wheels total. The same thing is going on here. One mole of H2, that's 6.02 times 10 to the 23 H2's. And there's two H's per H2. So it must be this number times 2, which is 1.204 times 10 to the 24 H atoms. So again, a little bit of a wrinkle compared to what we were talking about before. But this is also something you should ultimately have under your belt. A little bit more drilling, I have one mole of oxygen atoms. How many oxygen atoms do I have? 6.02 times 10 to the 23 O atoms. I have one oxygen atom and one hydrogen atom, which one weighs more? This goes way back to the beginning of this unit when I told you that the average oxygen weighs about 16 times more than your average hydrogen. So the oxygen weighs more. And there it is visually, there's your average oxygen. There's your average hydrogen. You can see that the one on the left weighs about 16 times more. I have a dozen oxygen atoms and a dozen hydrogen atoms. Which pile weighs more? It's this one because this is basically every single one of these oxygens probably weighs about 16 times more than every single one of the hydrogens and I have equal numbers of them. I have one mole of oxygen atoms and one mole of hydrogens. Which one weighs more? Obviously this one because all of the pieces weigh more. And you can look up in the periodic table. The one mole of oxygen weighs about 15.999 grams. And for our purposes, we're just going to round to the narrow-stool number, so 16 grams. So that's the end of the drilling, or at least the end of this drilling. We're going to cover a slightly new topic. We're going to extend the idea of a mole in the next video. So get ready. Get some rest. See you soon.