So, this is 4.58 times 10 to the 22nd molecules. Significant figures, because my whole calculation, that was my limiting significant figures, I have 4.58 times 10 to the 22nd. EE means times 10 to the, times 10 to the 23rd, is equal to that. So, let's just multiply this times 6.022. And so, but once again, because we did this whole calculation, we're going to wanna round everything to three significant figures. Number that I had before 'cause it's nice to beĪble to retain precision until you have to think about Now these are going to cancel out, and I'm just going toīe left with molecules. We could write 0.0761 moles, I'll write mole, times 6.022 times 10 to the 23rd molecules, molecules per mole. Multiply this times 6.022 times 10 to the 23rd. Mole has roughly 6.022 times 10 to the 23rd molecules in it, so we just have to How many molecules is that? Well, we know that each So, when we're multiplying and dividing, we just want to use the fewestĪmount that I'm dealing with. Slightly different colors, so n is going to be equal to 754 times 1.85 divided by 62.36 and then, also divided by, divided by 294, is equal to this thing. And so, let's get our calculator out to figure out the number One over one over moles, or it's essentially going to simplify to just being a certain number of moles. This Kelvin cancels out with this Kelvin. So times, what is 21 degreesĬelsius in terms of Kelvin? Well, I add 273 to that, so Is just one over mole, so I could write it like this. So this is going to be 62.36 liter Torr liter Torr, per mole Kelvin. You just have to add 273 to whatever you have in degreesĬelsius to get to Kelvin, because none of these are Given in degrees Celsius.' But it's easy to convert fromĭegrees Celsius to Kelvin. I know what you're thinking, 'Wait, the temperature's I'll use this versionīecause it's using all of the units that I already have. And then that is going to be divided by the ideal gas constant. And so let's multiply times the volume, so times 1.85 liters. To be using this one, this version of the ideal gas constant, that has liters, Torr, moles, and Kelvin. And here, they give the volume in liters in several of these, and we're probably going But for the purposes of aįirst-year chemistry class, you can view a millimeter If you get very, very, very precise, they are slightly different. But they do tell us that each millimeter of mercury is equal to a Torr. Of the ideal gas constants, you don't see any of them that deal with millimeters of mercury. They give us the ideal gas or the different versions And so this is going to be equal to what? Well, our pressure is 754 So, to solve for n, you justĭivide both sides by RT, and so you are going to get that n is equal to pressure times the volume over R times T, R times T. This little table here, that you might see on a formula sheet, if you were taking On which units we use, and we'll figure out I know what some of you are saying, 'Wait, do we know R?' Well, R is a constant. Here except for n, so we can solve for n. Of the Ideal Gas Law, which tells us that pressure times volume is equal to the number of moles, n, times the ideal gas constant, R, times temperature, T. That connects pressure, temperature, volume,Īnd the number of moles? Well, you might be thinking So they want to know, so we often use the lowercase letter, n, to represent the number of moles. They're also giving us, I'm trying to use all of my colors here, they're giving us a pressure. What they are giving us and what we need to figure out. How many moles of air are in the breath? How many molecules? So pause this video, and see if you can figure Athlete takes a deep breath, inhaling 1.85 liters of air at 21 degrees Celsius and 754 millimeters of mercury.

Stp chemistry calculator