 So, let's try this second one. It says calculate the wavelength of a helium atom whose speed is equal to the root mean square speed at 20 degrees Celsius. So, well, this is kind of giving us a clue as to say, what do we need to figure out? Well, what is the root mean squared speed of a helium atom at this particular temperature? So, in order to do that, of course, you need to know, well, what is the root mean squared formula? So, mu average or root mean squared is going to be 3RT divided by molar mass to the 1 cap, so the square root. Okay, so we need to know all this stuff. T has to be in Kelvin plus 273 into 293 Kelvin. R, well, that's going to be the 8.314 R joules per mole Kelvin, so that gives you a clue as to what temperature you've got. Molar mass. So, what did they say? This is helium. So, if we look up at our periodic table, it's going to be 4.03. Okay? We're going to have to get rid of joules and convert this to kilograms as well. You'll see that in a second. Okay? Remember, one joule equals one kilogram meter squared per second squared, like that. Okay? So, if you want to, let's take that formula here, this conversion factor, and make it just one line on each side. So, one joule second squared equals one kilogram meter squared. It'll be easier to use. Okay? So, if you see that just algebraically. Okay, so this kind of clues us in as to, well, we need this in kilograms. Okay? So, let's just do that in the problem. We'll just do it. Okay? So, here we've got three. So, R, 8.314 joules per one mole. And then what did we say? Well, we've got to convert. Okay? So, we want joules on the bottom. So, one joule second squared, one kilogram meter squared, like that. Okay? T, 293 kelvin, all divided by, well, what did we say? 4.03 grams per one mole, 1000 grams. We're going to take that all up to the one half. So, let's see what we can cancel out. So, joules cancels with joules, kelvin cancels with kelvin, moles cancels with moles, grams cancels with grams, kilograms cancels with kilograms. And remember, we're looking for average velocity, right? So, meters per second is a good unit. And that's what we got. Meters squared per second squared. And then we're going to take the square root of that. Okay? So, let's calculate this together. And I'm just going to leave this at whatever number of six things that comes up. So, three, okay? And then take the square root of that into there. And so, like I said, I'm going to keep this to as many six things as I want. So, 1351 meters per second. Okay? So, that's the root mean squared of a helium atom by itself. Okay? So, now we have to use the de Broglie equation to figure out the wavelength from the information that we got. So, do you remember the de Broglie equation? Okay. So, it's lambda equals h over m. So, that's what we just figured out here. Does that make sense? So, that's what we're going to put here. And what are we looking for? We're looking for this wavelength here. Okay? Okay. So, I'm going to erase this stuff here, so I can use that part of the book. Is that all right? Yeah, fine. Remember that, 1351. I'll write it in this email. So, well, what else do we need? We need to know what length's constant is. Okay? That's going to be given to you. 6.336 times 10 to the negative 34 joules seconds. Okay? Mass of a helium atom. Well, from the periodic table it's 4.003 negative mu. Right? But we're going to need this in kilograms. Okay? So, for every 1 amu, we get 1.661 times 10 to the negative 24th grams. Okay? So, that's a conversion factor that you're going to be given on the test. And of course, for every 1,000 grams, you've got 1 kilogram. Why are we doing that? Because we're going to convert into kilograms. Okay? So, let's see. Okay, let's start just plugging stuff in. And if we need to use anything else to convert, okay, we'll do it. Okay? So, let's figure out what this number is first. Okay, 4.03. So, 6.649. So, we're going to get this 10 to the negative 27. So, 9 equals 6.626 times 10 to the negative 34 joules seconds. Okay? But we want to convert joules so we can get rid of those mass units. Okay? So, remember our conversion factor from before on joules. Okay? So, we're going to use that. So, joules at the bottom, 1 joule second square, 1 kilogram meter squared. So, divide that by the mass that we just got. 6.649 times 10 to the negative 27th kilograms. Okay? So, we're going to convert times the root mean square to 13.51 meters per one second. Okay? So, let's start canceling stuff. Okay? So, kilograms cancels with kilograms. Seconds cancels with one second there. This second cancels with the other second there. Okay? Joules cancels with joules. Meters cancels with one of the meters and we're left with meters. Okay? So, meters, is that a good wavelength unit? Yes. Yes. Okay? Because it's a length. Okay? So, I'm actually going to convert this into a smaller unit. Okay? More than likely, picometers from what I can remember. Okay? So, we're going to multiply. Okay? So, I get 7.5 to the negative 10. So, remember this was actually the 3, so that's what we're going to use. 7.38 times 10 to the negative 11 meters like that. Okay? Well, let's convert this to picometers. So, for every one meter, you have 1 times 10 to the 12 picometers like that. So, cancel cancel. And that's going to turn this into 73.8 picometers. So, that's the wavelength of the helium atom at the root mean squared speed that it would be at 20 degrees Celsius. Are there any questions about that one? No. Okay? You just got to go through these formulas, dot, dot, dot, dot. Okay? Cool. I'm going to kill it. Yeah. Okay? So, I'm going to go through these formulas, dot, dot.