 Okay. So let's try to do this problem. This is an example of where you would have to use the Clausius-Clapeyron equation. Okay, so it says the vapor pressure of ethanol is 115 Tor at 34.9 degrees Celsius. Because if the change of heat of vaporization of ethanol is 40.5 kilojoules per mole, calculate the temperature degrees Celsius when the vapor pressure is 7,760 Tor. So again, let's write down what this problem gives us. So it says the vapor pressure initially is 115 Tor, and it also gives us the temperature initially. So T1, 34.9 degrees Celsius. And remember we always have to convert those to Kelvin. So in order to do that, add 273 to it, and that's going to be 307.9 Kelvin. It also gives us the change of the heat of vaporization of ethanol is 40.5 kilojoules per mole. It tells us that pressure 2, so we're trying to figure out T2 at T2, and it says that T2 is 760 Tor. So we're looking for T2. So hopefully you guys can see this and see that you need to use that Clausius-Clapeyron equation. So if you recall, we're comparing one thing to another, so we're going to use that second part of it. So ln of P2 over P1 equals the negative delta H bath over R times 1 over T2 minus 1 over T1. Okay, this R here is the ideal gas constant when it's sold for joules. So on R, this is going to be given to you 8.314 joules per mole Kelvin. And in fact that's why we had to convert the temperature to Kelvin is to cancel that out eventually. So again, like I was saying before in the last problem that we did, normally I would have you isolate the variable, but in these types of problems, it can get a little hairy when you're trying to do that. So what I probably just have you guys do is just plug them all in and then chug it all out. Okay, so let's do that together and we'll cancel out all our units while we're going through the problem. So ln of P2 760 tor divided by P1 115 tor equals negative delta H bath 40.5 joules per 1 mole. So that's divided by R, we could say 1 over R. So in that case it would be 8.314 joules per 1 mole Kelvin like that. Okay, and notice this is kilojoules and this is joules so we're going to have to cancel those out. So we're going to have to convert one to the other. Let's convert the kilojoules to joules. So 1 kilojoules is 1,000 joules. And now we're looking for 1 over T1 is 07.9 kilo. Okay, so why did I do this? The inverse of R is because it's 1 over R here. So let's go ahead and cancel out all our units. So tors cancel there, moles cancel with moles there, kilojoules cancel with kilojoules there, joules cancel with joules there. So let's just go ahead and figure out what all of these numbers should be. So 716 divided by 150. So this has no units associated with it, right? Equals 40.5 divided by 2. What we can do is divide both sides by that negative number, right? Okay, so that's going to cancel there. 7, 7 times 10 to the negative 4 equals 1 over T2 minus 1 over... If you want to figure out that one, you can, right? So 07.9 is per 1 kelvin, right? So we've got our units the same. Is everybody okay with what we're doing? Now we're running out of board room, so would anybody be opposed to me erasing the top of the board up here? Okay, so what do we have now? Now we've got 1 over T2 negative 3.877 times 10 to the negative 4 times 10 to the negative 3 per kelvin. Number 2.60 times 10 to the negative 3 per kelvin. So that's 1 over T2. So in order to get T2, right, we've got to do 1 over that number. Is everybody okay with that? So T2 equals 1 over that number, so 49.6 kelvin. But it asked us to give it in degrees C, right? So how do we do that? Minus 273, 76.6, okay? So in other words, at pressure 760 Torr, the temperature is going to be 76.6 degrees C. Is everybody okay with that? Any questions on that one? I know there was a lot of steps, okay? So again, remember, canceling your units out really helps, okay? So, okay, so good job, guys.