 Okay, so this first solubility question says if the molar solubility of calcium fluoride at 35 degrees Celsius is 1.24 times 10 to the negative third moles per liter, what is the Ksp of calcium fluoride at this temperature? Okay, so we have written up here the molar solubility, so remember molar solubility is moles per liter just like molarity, okay, and it's 1.24 times 10 to the negative third, and that was given to us in the problem. So if you recall, the first thing we have to do is write the chemical equation, remember. So when we're looking at this number here, that number is referring to this calcium fluoride, so we're using this chemical equation to get information from using that number here. So what does that mean? Just like stoichiometric relationships. That's the precipitation equilibrium, and now we want to figure out, well, what's the concentration of each of these particular ions given the concentration of calcium fluoride, okay? So why would we need to do that? Do you remember? Because we're looking for Ksp, so in this case the Ksp equation is going to be what? Ksp concentration of calcium ions times the fluoride ions, and what? We're going to put up here? Squared. Squared, right? And we get that from the coefficient there, right? Okay, so that's why we need to know, well, what is the concentration of these calcium ions in the fluoride ions? So you could go through the entire calculation, but I'm assuming you can do this in your head by now, right? So the concentration of the calcium fluoride is going to be equivalent to the concentration of Ca2+, right? Because we have a 1 to 1 ratio, and the concentration of the calcium fluoride is going to be equivalent to 2 times the fluoride ion, okay? So when we do this, this is going to be 1.24 times 10 to the negative third molar, and this is going to be 2 times that number, so what is that? 2.48, right? Do that right without a calculator, pretty amazing. Okay, so Ksp, that's what we're looking for at 35 degrees Celsius, right? So we have the concentration now of fluorine, right? And we have the fluoride ions and the concentration of calcium ion, so all we're going to do is plug those into this equation here. And here, if you recall, all the equilibrium constants have no units, okay? So if you want to put your units in, that's fine. Just remember to cancel them out later, okay? But I'm just not going to put them in, just so we won't confuse ourselves. So 2.48. So now just get out your calculator, and you should be expecting this to be a small number, right? Calcium fluoride is not soluble. And I get to 3 6 pigs, 7.63 times 10 to the negative 9th for the Ksp of calcium fluoride at 35 degrees Celsius, okay? So remember, no units, okay? So you don't want to have units of like molarity cubed or something like that. Okay, does that make sense? Okay, cool. Any questions on it? No? Okay, certainly.