 So, 6 says, if a balloon filled with di-nitrogen tetroxide gas at 500 degrees Celsius and 0.87 atm is cooled to 128 degrees Celsius, what is the new pressure of the N2O5 gas? Okay? So, we know some things about it already, right? We know the initial temperature, right, so that's T1 is 500 Celsius and we know P1, too, right? It says it's 0.87 atm. What else do we know? So, T2, right, the temperature that it changed to, 128 degrees Celsius, and P2, it asks, well, it asks, what's the new pressure of the gas, right? So, that's what it's looking for. Now, remember to get this, you don't have to remember all of those laws, you know? You just have to remember the ideal gas law, and that's PV equals nRT, right? And you just do 1111 and then divide it by PV equals nRT, but 2222, okay? And then you ask yourself, did P change? Yes. Yes, so you can't cancel that out, right? Because P1 does not equal P2, right? Did V change? No. So what does that mean? If V did not change, then that means V1 equals V2, right? So essentially V1, or V1 is V2, right? So if that's the case, we can cancel both of those out. That makes sense, right? Did the number of moles of gas change? No, so it's the same argument, right? n1 equals n2. Does R ever change? No. So that can cancel out. So we've got this new equation, right? So what's our new equation here? P1 divided by P2, very good. This T1 divided by T2. T1 over T2, very good. And what are we looking for, P2? So we want to isolate that variable. We could do it a number of ways. The way I like to do it is just flip it over, right? And then just multiply by P, both sides by P1. But let's flip it first, okay? So now we've got P2 on the top. So what we do to one side, we've got to do to the other side. And then, of course, we want to isolate the variable P2. So we're going to multiply by P1, right? Because P1 is being divided by P2. So what's our new equation? P2 equals, yeah? Very good. And you want to think about it this way. So the temperature decreased, right? Would you expect the pressure to increase or decrease? You'd expect it to decrease. So you would think that it would be less than 0.87 ATM, okay? The other thing that you want to do is get this in kelvin, okay? So do you remember how to do that? Yeah, add 273. So that's going to be 773. And then, so now we're in kelvin. So that's absolute temperature. So now we can plug that in there. So we always want to remember, we've got to change that to kelvin. Because Celsius will go negative and positive, and that'll mess up, you know, your calculations. So anyways, I'm just going to put it over here so we'll have more room to plug and check. So P2 equals, well, T2, which is 401k, P1, 0.87 ATM. It's very similar to what we were doing today, remember? Yeah. And in fact, you'll see that it's very, very similar to the things that you just keep repeating the same thing. And then T1, of course, is going to be 773 kelvin. And of course, kelvin cancels leaving you with ATM. Right? Would you expect ATM to be your unit? Yes. Because you're looking for pressure. Okay, so you want to always keep all that stuff in mind. So you have 401 times 0.87, and then divide that by 773. Now remember, we thought it should be less, right? Yeah. And in fact, it is, which is cool, and it should be the two sick foods, right? Because this one is two sick foods. Okay. So when I get it, I get 0.4518. Does it make sense? Yeah. Oh, we did? So you just want to do it stepwise. All of these are stepwise things. And if you're not, you know, if you're skipping steps or things like that, you're going to mess up, you know? And the other thing you want to ask yourself is does my answer make sense? It went down, you know? You would expect it to go down. From hot to cold, you know? Here, if you put a balloon, it's going to, you know, decrease in pressure and put it in the cold. Okay, cool.