 Okay. So, I'm making up a problem now. So, using this reaction equation showing the decomposition of mercury 2 oxide, we, at the end of the reaction, weigh 20.42 grams of mercury. How many grams of mercury 2 oxide did we start with? Okay, so we're going to do this problem. So, the first thing I have to do is convert. So, this is 20.42 grams of mercury. But we don't know that then here. Already. And then I got to convert this to number of moles. So, what's the conversion factor? The mole or mass, right? I know you guys remember that. So, if I look up at the periodic table, I can get that number, 200.59 grams of mercury per one mole of mercury. So, that cancels that. Is everybody okay with that? So, now we're on that moles of mercury. Everybody cool with that? So, Shelby, this is what we were doing at the end of when we had to come in here. Okay? So, this is the step where we were on. So, now I've got to figure out, well, how many moles of mercury 2 oxide do I have knowing that I have that many moles of mercury? Okay? So, I have moles of mercury calculated already. So, I want to convert that. I get that conversion factor from the chemical equation like was said earlier. Okay? So, I'm going to multiply that by the conversion factor that I find in the chemical equation. So, I want to cancel out moles of mercury. So, what do I put at the bottom? Moles of mercury, right? And the coefficient tells us what the mole to mole ratio is, right? So, the coefficient for mercury here is what? 2, right? 2. So, 2 moles of mercury, like that, right? Equals, because we're trying to figure out mercury 2 oxide. How many moles of mercury 2 oxide would that be? 2, right? That's the conversion. Is everybody okay with that step? What do we do now? Cancel. And we're left with units of what? Moles of mercury 2 oxide. Is everybody cool with that? But remember, we were looking for grams of mercury 2 oxide, right? We weren't looking for the number of moles of mercury 2 oxide. So, I need a number that's going, or a conversion factor, I should say, that's going to change from what? Moles to grams. What is that conversion factor called? The molar mass. The molar mass, okay? So, and specifically, it's going to be the molar mass of mercury 2 oxide, right? So, how do I figure that out? Look at the periodic table, right? So, mercury 200.59. Now, since I'm doing the molar mass, I can switch those units without going through that long calculation that we did previously, recall, right? So, I can say grams per mole. Is everybody okay with me doing that? And then I'm going to add that to, well, 1 oxygen. I'm just going to do it to 2. So, 16.00 grams per mole. Is everybody cool with me doing that? So, this is going to end up being 216.59 grams. Good with that? Finding the molar mass of mercury 2 oxide? Okay. So, can that units up there convert moles to grams of mercury 2 oxide? Would that be possible to do using that unit? I wouldn't lead you down the wrong path, especially when we're recording it. Okay. So, what is that conversion? What am I putting down here? What is units? One mole. Okay. That's the one mole with the number 2, right? Yeah. So, units would be moles of mercury 2 oxide, but you're absolutely right. The number would be 1, right? Because this is divided by 1 mole. And what would be up here? On top, 216.59 grams of mercury 2 oxide. And then I do what? Cancel. Should that give me the mass of mercury 2 oxide? Yep. Okay. So, now all we do is plug a jug, right? 20.42 divided by 200.59. 2 divided by 2 is 1. So, I'm just going to skip that and then multiply by 216.59, bless you. And I get, and I want this to be 1. So, I'm going to do 4 sick fix. Is everybody cool with that? 4 sick fix? And I get 22.05 grams of mercury 2 oxide. Could you guys do something like that on your own? So, I want you to know that that's exactly how you were to do that last problem. So, again, if you wanted to do this, you could do this. Or you could do the kind of training method that I just did. Cancel and all that. The major things that you learned in this chapter already and are going to take away is the molar mass is a conversion between grams and moles, right? And the chemical equation is a conversion between moles of one substance to moles of a different substance. Is everybody okay with those concepts? Okay, good. Question?