 So let's go ahead and do this problem. So what did we say? We said We got this chemical equation here that says two mercury two oxides Decompose so hopefully you guys see this is a decomposition reaction, right? So every reaction you guys should be thinking about all of this stuff that you'd like. But anyway Mercury two oxide decomposes into giving you two mercury's and one oxygen molecule Okay, so that gives us a lot of information in that chemical equation So what our problem says is? We've got 1.43 grams of mercury two oxide What is the total mass of oxygen that will make if the reaction goes to completion? So the first thing we're going to have to do is figure out what the mass of mercury two oxides Okay, so when we do that we got it. How do we do that? We look up at the periodic table, right? We say okay. Well mercury is here 200.59 And we add that to oxygen I'm just going to say 16 and we get for remember the molar mass of mercury two oxide we're going to say 216.5 9 Grams per mole Okay, so with this information here The mass of mercury two oxide. We should be able to get the number of moles of it Everybody okay with where I'm going with this? So let's do that. So the number of moles of mercury two oxide is going to be the mass times the inverted molar mass Okay, so remember I said this is kind of the one line way of writing or the text message way of writing it So if we're going to really make it functional We're going to write it out like that Remember this is a ratio whether we have it this way or flipped upside down So let's just flip it upside down and use it properly So we can get those grams out of the way So we got one mole is 216.5 Like that Okay, remember this is moles of Mercury ox So what is the chemical equation tell us remember we're looking for oxygen the mass of ox So what do we know about the number of moles of mercury oxide relative to the number of moles of oxygen that we're going to make Two to one ratio right so remember Just like what we said in the before we turn on the video. We can make another conversion factor out of that right so to HGO or we'll say two mole HGO equals One mole oh two So what do we do here? multiply So now we're not doing the number of moles of mercury oxide right we're going to find the number of moles about two so we've got two moles Mercury oxide One mole oh two like that So what did we do before or what are we doing now? cancel Cancel to find the moles of oxygen So everybody okay with what we've done remember it's like going across a river Step on the next stone step on the next stone if you try to jump to the very last stone You'll probably jump into or fall into the river and float downstream. Okay, but this is not what we wanted Right, what did it ask for the mass of oxygen or the grams of oxygen? Okay, so this is the moles of oxygen so instead of the number of moles so n is like the number That's why I'm using it. Let's look for the mass of oxygen Do we know something that converts the number of moles of oxygen to the mass of oxygen? What is that? What is it called? Not the box again. It's called the molar mass right the molar mass. Okay, so It's going to be well 16 times 2 right, so it's going to be 32 So what do we know? the molar mass O2 is going to be 32.00 grams per mole that we've got one mole O2 32.00 grams O2 Cancel cancel and is that what we were looking for the mass of O2? At least play cake me guys. Tell me. Yeah, right. Okay, cool. So if we do that, right? What are our units here? Grams of O2, right? Let's calculate it now. So 1.43 times 32 divided by 216.59 Divide that number by two and I get the number 0.10 1056 and is that the right number of sick fix? No, because we started with three over here So 0.106 and then we'll just move this Grams of O2 Like that. Okay, and of course you can put that in the scientific notation if you prefer. Do you know about 0.106? That's a pretty reasonable number to be able to read. Are there any questions on anything like this? Again guys, I know it seems like a lot, but you know Every time you've got a ratio, it's a conversion factor and now you know The chemical equation could be used as a conversion factor The other thing that's very important is to remember all their masses convert moles to grams grams to moles Okay, so you can use that going from grams to moles here But remember this only tells you moles to moles Okay, so you can't do like what you were trying to do at the beginning and say because we got this many grams of this Well, we have half of that many grams of oxygen because they weight different amounts Okay, it's like saying, you know, I Don't know I could make up an analogy, but I don't want to ruin the video. So are there any questions? Okay, cool