 That wasn't so bad to set back up, huh? OK, so let's start with the problem that we finished with last time. So remember, of course, we're calculating concentrations of solutions these days, OK? So, volality is, again, a concentration unit. Remember, it's little m, right? And it's the same as molarity. And it's the number of moles of solvent, or solute, on the top in the numerator. But instead of volume of solution in the denominator, it's going to be the mass of the solvent in kilograms. So mass in kilograms of the solvent. So again, sometimes this messes people up because little m is both mass and molality, OK? So watch out for that. But sometimes it's written like it's written up there where it says kilograms, you know? So it's a little easier. So whatever you think is the easiest way to think about it, go for it. So let's go ahead and do this problem. It says calculate the molality of a potassium chloride solution containing 52.3 grams of potassium chloride and 3.01 kilograms of water. So we know two things, right? Well, we know three things that it wants us to calculate the molality, right? But it gives us the mass of both potassium chloride and water. So the mass of potassium chloride is going to be 52.3 grams. And the mass of water is going to be 3.01 kilograms, OK? So I guess the first thing we got to decide is which one's the solute and which one's the solvent, right? So which one do you think is the solvent? The water, right? Why? Makes more sense to be the solvent for an introductory chemistry problem because that's the only solvent you guys know, but not to mention that KCl is the what? The solvent, right? And water is a liquid, right? So it makes more sense to dissolve. Not to mention KCl is an ionic solvent, right? So ionic solvent solutes dissolve pretty well in polar solvents like water. Remember all that stuff. OK, so we got the mass of the solvent then, right? So the mass of the solvent and kilograms. And that's what we're looking for, right? So let's just go ahead and put that down already. So the other thing we need, though, is the number of moles of the solute, right? So since KCl isn't the solvent, it must be the solute, right? So we're looking for the number of moles of it, right? Is that the same thing as grant? No, right? No, of course not. I like the responses being like, what? So how do we figure out how many moles of KCl we've got? Use the what? The molar mass, yeah, very good. Why? Because that converts from what to what? Grams to moles, right? So we need something that's going to convert from grams to moles, right? And we're going to put the what on the bottom. The grams, right, very good. And the moles on the top, right? And in this case, it's going to be one mole because it's the molar mass, the mass of one mole. And how do we figure out the molar mass? Well, we look at the periodic table, and we look at the atomic weights of these things. So potassium is 39.10, and chlorine is 35.45. We add those two things up, and we get 74.55. Grams of potassium chloride per mole of potassium chloride. So we can cancel out grams there, and that's going to give us the number of moles of potassium chloride. So we just do 52.3 divided by 74.55, and the number of moles, 0.7, because it's the 3.6, right? And then we'll just plug that number in here. And remember, this is so little m, or molality. It's easier to look at it from back here sometimes. So remember, molality is like the shorthand way of writing this, moles per kilogram. So all we've got to do is take that 0.702 and divide it by 3.01, and we get the same number we got on Wednesday. We just say little m like that, and that little m means, or we call it molar. So 0.233 molar is the way we would say it. Is everybody OK with that? We'll set that one up.