Jules Bruno
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Hey, guys, In this new video, we're gonna continue with our discussion on calculating mawr equilibrium concentrations. So if we take a look at this first one, it says if Casey is 32.7 at 300 degrees Celsius for the following reaction, the reaction is to one mole of H two gas plus one mole of BR to gas gives us two moles of H P R gas. What is the concentration off H two at equilibrium? If a 20 liter flask contains five moles of h br initially. Now what we should say to ourselves is Do I have to do a nice chart or not? What we should realize here is all I'm giving you is initially Onley this amount of product so we don't have anyone in equilibrium. And therefore we have to do a nice chart. Remember, if you're missing mawr than one compound at equilibrium, you must do a nice chart. But something's weird about this particular question. We're used to seeing initial amounts for our react. It's and we're used to seeing zero amounts for our products. This one's actually written backwards. So what we're gonna do here is we're actually going to flip this reaction so that it makes more sense. We should initially have some reactant and then our products are normally at zero initially and it's gonna be ice chart, because again, we only have the initial amount of now are reacting HPR. And remember, we're doing this because again we're used to seeing initial amounts for our react. It's not our products and realized if we reverse the reaction, then this is gonna change. What are K value is Just remember here, reversing the reaction will give us the reciprocal of K. So now Casey becomes 1/32 0. and that answer is going to be 3.6 times 10 to the negative, too. Now, what we're gonna do here is we're going to say initially, how much reacting do we have? We have five moles and we're gonna divide it by 20 leaders. And remember, we're doing this because the units we can use in a nice chart on polarity or atmospheres. Since we have moles and leaders in this question, that's gonna help us find mole Arat E. So that's gonna be point 25 Moeller. So that's our initial amount. I don't tell you anything. Initially about are reacting. So there's zero. Remember, we're losing react INTs to make product plus X plus x. This is gonna be 0.25 minus two acts plus X plus X. Now what we're gonna do is we're going to solve for X variable. So now we're gonna say that K C equals products overreacting. So it equals h two times br to over HBR squared and it's squared because remember the two here. Now we're just gonna plug in the numbers. We know we know what Casey is. It's 3.6 times 10 to the negative, too. That's gonna equal at equilibrium H two and B R two are both x so x Times X is gonna give me X squared divided by yeah, 0.25 minus two x squared. Now remember, we have toe isolate our X variable, but the problem is, sometimes we'll have to use the quadratic. There are two times when we can ignore the we can get around this limitation. Okay, so there's two times we will be able to manipulate the equations so that we can avoid the quadratic formula. This happens to be one of those times. Remember, we've talked about this before. We have the perfect square method here. Remember, The perfect square method means we have the top is squared in the bottom of squared. And since both top and bottom r squared, I can take the square root to avoid the quadratic So square with this square. With this, that's going to mean my answer now is 0.175 equals taking the square root of those squares just gets rid of the squares. So it's gonna be X over 0.25 minus x minus two x multiply both sides by 0.25 minus two x 0. minus two X. Now you're going to distribute distribute, since we're gonna need some more room to work this out, guys, I'm going to remove myself from the image so we have more room to work with. Okay, so now we're gonna have 0.4375 And remember, how do we get that? The 0.175 multiplied times the 0.25 when we distribute it minus 0. x equals. It's still equal to x Group. The X variables together. Okay, this X is actually one X we're gonna add 0.350 x to it. So I'm gonna say 0.4375 equals 1.350 x divide by 1.350 on both sides. So we're gonna say here that are X equals 0.3 to 4 Moeller. Now, remember, we shouldn't just circle this, so we're gonna take away that circle. We shouldn't say that this is our answer. We have to look and see. What did they ask me to find an equilibrium? They're asking me to find hte to equilibrium. If we go to the equilibrium line, we see that indeed H two equals X. So this answer we just found is acceptable. But remember, if I had asked for the equilibrium amount of HB are at equilibrium, we would take this X and plug it in here and then find the correct answer for HBR. So always be careful. Just because you find X, that doesn't mean that's your answer. Check to see what you're asked to find and then check to see what it's equation is on the equilibrium line. That's the best approach you want to take. Now that you guys have seen that one, I want to see if you guys can try to tackle this particular question. We're gonna say at a given temperature, the gas phase reaction H two gas plus O two gas gives us to. And actually we're gonna change this H two to a nitrogen two and two plus Gas gives me too, eh? No gas has an equilibrium constant off 4. times 10 to the negative. 15. What will be the concentration of Eno equilibrium if two moles of nitrogen and six moles of oxygen are allowed to come to equilibrium in a two liter flask? So what we need to realize here is do we need to do a nice charter or not? Once you guys figure that out, I want you guys to at least attempt to do this. Don't worry. If you don't know where to go with it, just click on the explanation button and I'll appear and I'll be ableto answer it. Look at the strategies that I use in order to solve this particular one. Good luck guys attempted on your own First. If you get stuck, go and click on the explanation button