 Okay, so the compound carbon disulphide, what did we say the molecular formula was? CS2. Okay, we get that because carbon disulphide, right? That's a covalent compound, right? Because they're two non-methes, right? Two or more. I wanted to say what is the molecular weight? So covalent compounds are molecules, if you recall, right? I wanted to say what's the molecular weight of this? Could I figure that out? Yeah. How would I go about figuring that out? If you're on a table to find the average... Not the average. Yeah, the atomic weights of carbon plus two times the atomic weight of sulfur, right? Yeah. So what would be the units here? They tried it. I know that all of you have calculators out, but don't always try things. Okay, so this is the mass of one molecule. Is everybody okay with me saying that? So what if I wanted to figure out, in AMU, the mass of one mole of molecules? How would I do that? What is one mole? What is that? That's not that number. No. Does anybody remember? What was that? Yeah, so it's Avogadro's number, right? A mole is Avogadro's number. What is Avogadro's number again? Right? So just like a dozen is 12, Avogadro's number is 6.022 times 10 to the 20th. Something I'll give you, okay? So if I have a mole of pencils, right? It's 6.022 times 10 to the 23rd pencils. If I have a mole of carbon disulfide molecules, 6.022 times 10 to the 24th carbon disulfide molecules. Is everybody cool with that? So what if I said, how much does four carbon disulfide molecules weigh? How would I figure that? Avogadro's number? No. No. By the what? Mass of one of these molecules, right? So I multiply that by four and I would get the mass of four, right? What if I wanted to get the mass of a mole of them? What would I do? What would I do? Multiply it by what? Avogadro's number. Does everybody understand that, right? So I need more interaction from you guys. So what I'm trying to do now is figuring out the mass of a mole of these things and I'm going to do that in AMU first, okay? So in order to do that, I have to multiply it by Avogadro's number. Is everybody cool with that? So the one thing I want you to remember about Avogadro's number is there is some units associated with it because it's that per mole. Okay, you don't always see those units associated with it, but it's like if I said I have a dozen pencils, right? It'd be 12 per dozen, okay? 12 pencils per dozen, okay? So just like this is 6.022 times 10 to the 23rd per mole. Okay, is everybody okay with thinking about it like that? Okay, so just one mole equals, so I say, is everybody cool with that? So let's figure that out. So I just multiply it by 6.022 and I get, should I get a big number or a small number? A very big number. 25 AMUs per one mole, okay? Okay, this is a very cumbersome number, right? Why is that? Because moles are a big amount, right? Very big amount relative to AMUs, right? AMUs are a very small mass unit. Does everybody understand what I'm saying? So moles are kind of more on the level of humans being able to see them as opposed to just little molecules or atoms or something like that. So we want to convert this mass into a mass unit that we're more familiar with, okay? So a good mass unit might be grains, right? So there is a conversion factor that I don't expect you guys to remember, but some of you were trying to tell me it when I was asking for Avogadro's number. But it's 1.661 times 10 negative 24 grams equals 1 AMU. Okay, yes. I will give that to you every time. Yes. I looked up how to do it. It basically said just take the Av and then divide it by the amount of grams. Let's just do this, okay? So we've got a conversion here, right? Okay. So we want to take our AMUs to grams. So what are we going to put at the bottom here? AMUs, right? And the number associated with those AMUs? One. And up here? 1.661. Yeah, very good. Right? So when I do that, so cancel, hopefully everybody sees that. Okay? So I'm going to multiply this times this, 0.66188. And I get a number that is 76.15. And look at my unit, grams per mole. Okay? So that's how many grams a mole of carbon disulfide weighs. Okay? If I would have taken these things all the way out to all the digits, this number and this number would be exactly the same. Is everybody okay with that? So a shortcut to do this, instead of doing all of this, which I don't expect you to do every time. In fact, if you're doing this every time, you're missing the point. Okay? We do want a shortcut for this, okay? The shortcut is that whatever this number is in AMU that you get off the periodic table, you can also be the same number for your molecular weight, or your molar mass. Pardon me, your molar mass, okay? So the only difference is what? The unit sort of change. Is everybody cool with that? You got it or no? Yes, yes. Yes, okay, good. So again, do we have to do this every time? No. What can we do? Just look at the cheat sheet up there, right? The periodic table. So you can have that for everything that you do in this class, okay? So can I kill this one?