 Okay, so let's go over this problem that we went over in class. Calculate the maximum amount of SO2 that can be produced by reacting 55.2 grams of oxygen with 50.8 grams of hydrogen sulfide. So the first thing you need to do is write the reaction equation. Hydrogen sulfide, in this case you probably won't know what the physical states of these particular molecules is. So you don't necessarily need to realize that. So hydrogen sulfide plus oxygen, that's what it's saying because those two things are reacting together to form SO2. So notice we want to balance our equation now, right? So we got two oxygens on this side, two oxygens on that side. One sulfur on this side, one sulfur on that side, two H's on this side, no H's on that side. So if we remember hydrogen, you should remember how to build H2, right? But hydrogen prefers to be a diatomic molecule, a diatomic element. So H2 would be the last thing that we're missing in this reaction equation. Lucky enough, our reaction equation is balanced by not having to put any coefficients, okay? So all of our conversion factors are a one to one ratio, right? So now let's write down, well what do we got? It says that we've got 55.2 grams of oxygen. So the mass of oxygen is 55.2 grams, okay? Then it also says the mass of hydrogen sulfide is 50.8 grams. So everybody's okay with what we've done so far, right? This is all essentially information that has been given to us by the problem. Okay. So unfortunately this does not tell us the grams to grams to grams ratio. It tells us the moles to moles to moles ratio. So we're going to have to do something to these numbers to convert them from grams to number of moles, okay? So we got to go back and remember how do we do that, okay? Well we need to know the molar mass of these two compounds or in this case molecule. The molar mass of oxygen is 32, yeah, 32.00 grams per mole, remember? And the molar mass of H2S is essentially 32 plus 1 plus 1, right? So I guess it's going to be around 34.7, I guess, right, 34.07, we'll say. If somebody has a better calculator than what I have in my head, you can tell me what the actual answer is, 34.02. It's got to be at least 0.06 or at least from what this periodic table says. Anyways, let's just use that as the molecular molar mass, it doesn't matter. Now let's figure out, well, how many moles of these two things we got, okay? That's the next thing we've got to do. Remember, I'd like you to attempt to do these on your own without watching me because of course, of course I make mistakes, that's why. So if we do that, that gives us the number of moles and I got 1.725 moles oxygen, okay? And now let's try H2S, what did we say, 34.07? And again, I'm using 34.07 here and I got 1.491 moles H2S. Okay, so how do we figure out what's the maximum amount to get that? Okay, good. That sigh, I didn't know if that was a good sigh or a bad sigh, yeah. Okay, so let's try to figure out, I know it says the maximum amount, okay? So when it says amount, that means number of moles, okay? It would say what's the maximum mass or something like that if it was talking about grams, okay? So number of moles, what's the maximum number of moles of SO2 that we can make? Can somebody tell me, do you think you know already? And how would we figure that out? I can tell you one thing, all the information that you need for this question is up on the board to answer this question. How would you figure out what's the maximum amount of SO2 you can make? Why would the H2S be limiting? That's absolutely right, but why would it be? A smaller amount, but the ratio is the important thing, it's a 1 to 1 ratio, right? So since it's a 1 to 1 ratio, you can directly compare those two numbers, okay? If it were like a 2 to 1, you would have to do some manipulation to it, okay? The way you want to really think about comparing them is to say, well, how many moles of oxygen do I need with this? What you would do maybe is use your conversion factor that you already know. 1 mole of H2S to 1 mole of O2. Obviously this is just for posterity doing this, you know, so you can see which one is bigger. You can put your units on there, right? So you can directly compare these two numbers. Again, if it was like 2 moles of O2, then you would have a different number here, right? Okay, so now we want to compare really these two numbers here. Which one's bigger? This one, so the smaller one is going to be the limiting reagent. So this will be our limiting, well, this here is our limiting amount of moles, okay? So we've just figured out our limiting amount of moles. But we still don't know how many moles we could make of SO2, right? Could somebody tell me how to do that? How many moles of SO2 could we make? How about that? That might be an easier question to answer. Yeah, so what number is that? 1.491. Yeah, 1.491 essentially. Well, we're going to have to cut it down to three sig figs eventually, right? But the way you would do that problem is not, remember, you want to do everything mathematically. I know you can do that in your head, but for some of them it's going to be like a 3 to 2 ratio or a 4 to 5 ratio or some weird ratio that you're not just going to be able to do, oh, just multiply it by 2 or they're the same number. Okay, so you always want to get into the habit of taking what you got, 1.491 mole H2S and multiplying that by your conversion factor. Okay, what's your conversion factor? 1 mole H2S to 1 mole SO2. Moles H2S cancel out giving us 1.491 moles SO2, right? Cut that down to three sig figs and that's our answer. That's the maximum amount that we could have made, 1.49 moles of SO2. It makes sense how to do that, right? Just do one thing, then one thing, then one thing, just step by step by step. Remember, when I am, you know, like trying to decide how, for example, you know, if I'm standing right here. How in the world am I going to get to the other corner of the room, right? I don't think, man, that's going to be impossible for me to like jump over there, you know, I can't possibly do that. That's not, I don't even, that thought never crosses my mind, okay? So when you get a problem, you don't want to think, how in the hell am I going to find the answer? Because you don't think that you're not supposed to think that way. It's just like my walking across the room. I don't think, how in the heck am I going to go jumping over there? I just take one step at a time. I'm just all, look how casual I'm being, you know? Just walking around, walking to the other side of the room. That's what I want you to do with your problems, okay? Just take a casual approach to them because you know how to put one foot in front of the other, right? But you don't know how to fly like Superman, okay? And I don't expect you to, okay? Learn conversion factors. Conversion factors are all given to you in these problems. They're all given to you. You have to maybe balance some equations. You should be able to be doing that by now. And you might have to figure out some molar masses. You should be able to be doing that right now. Those are the only two conversion factors that you're going to be needing for advanced types of problems. These are the most advanced types of problems that you'll be doing, okay? Let's just do, keep this problem going for one more step and say, well, how many grams of SO2 did I make then, okay? Just to push it one more step. And then you could think about, well, what if the problem said, what's the maximum amount of grams of SO2? Then you could do that. This would be the hardest type of a problem that I could give you like this, is if I said this, calculate the maximum amount of grams, okay? And all you would have to do is one more step. Oh, pardon me. All SO2, cancel 95.5 grams SO2, okay? Hopefully you were able to get that on your own. Are there any questions before I call that one quits? Okay, yeah. I'm going to erase it. I'm just going to turn off the recording.