 Okay, so it says, your patient's oxygen tank reads a pressure of 52.2 millimeters of mercury with 10 liters of oxygen remaining. If the temperature of the tank is 98.2 degrees Kelvin, or 98.2 Kelvin, how many moles of oxygen are there left in her tank? So this is the PV equals NRT problem. So let's just write the things down that we know. Like you did. You started it out correctly in my bed. So P, well you got that right, 52.2 millimeters of mercury, but that's not the one that you want to use, right? And R, R is given to you right there. Just like in the practice exams, you know? I told you I wasn't going to make you memorize R, you know? So PV, what was V? 10 liters, 10.0 liters. Temperature, 98.2 Kelvin. So that's in the right units, that's in the right units. And moles. That's what you're looking for. And R, you know. Let's just go to the front page just to show everybody where it is, right? 0.0821 liter ATM, and I've memorized it, so divided by one mole Kelvin, okay? So that's the way I like to write it, because it's the expanded way, right? So we've got PV, P, and R, right? And nothing changed, right? So we're just going to use straight up PV equals NRT, okay? So how do we do that? PV equals NRT. Isolate the variable. Which variable do you want to isolate? N, right? How do we do that? Divide both sides by RT, right? Cancel, cancel, cancel, cancel. What do we get? N equals PV divided by RT, right? So let's just plug and chug. Well, we can't yet, right? We've got to convert that. So do we got a conversion factor? Probably, right? Because I told you you wouldn't have to know that one. So it's 760 millimeters of mercury divided by, or 1 ATM divided by 760, right? So we'll just take 52.2 divided by 760, enter, and I get, I'll just do it in scientific notation, 6.8. 7 times 10 to the negative 2 ATM. Why? Because millimeters of mercury cancel up, okay? You can look at it differently. Okay, so now we plug and chug, right? So P, we've got, we just got, 6.87 times 10 to the negative 2 ATM. V, 10.0 liters divided by R, which is given to us. 0.0821 liter ATM, 1 mole Kelvin, and then temperature, okay? 98.2 Kelvin. And you know if you've done this right, if your units cancel up, right? So Kelvin will cancel with Kelvin there, right? Because this is on top, that's on bottom. This is on top, that's on the bottom, that'll cancel with that. On top, on the bottom, cancel with that. 1 over 1 over the thing goes up to the top, if you remember in math. That's what we got, 1, right? No units up here, no units there, only unit is there. So that equals the units of moles, right? And all we gotta do is plug in our values. So, got that, multiply it by 10, divide it by R, 0.0821, enter, and then divide that by 98.2, enter. And the number of moles, if you want to, I'm gonna put it into scientific notation. Well, I'll write it out normally, and then put it into scientific notation, or write it out what the calculator gives. 5, 2 moles of O2 if you really wanted to, okay? And then to put it into scientific notation, because that's what we do in chemistry class. But if you didn't, I would still give you all credit for it. So 8.52 times 10 to the negative 2 moles O2. So again, I'm convinced that you could do this problem much faster than we do it together, you know? Because we don't have to explain to each other everything, you know? I would expect that problem to be done in about five minutes, something like that, you know? I think that you need to remember that you need to convert this, that's the big thing. And then when you read the problem, you see that the problem doesn't say anything about things changing, right? So since it doesn't say anything about things changing, you just do pv equals nRT. Remember, if it changed, it would be pvp1v1 equals n1RT1 over e2v2 equals n2R over TT. Is that cool? Okay, so do you understand everything? Is there any questions on that one? Okay, cool.