 OK. So let's try this last problem, this fourth one. So it says 9.45 grams of methyl alcohol CH3OH was dissolved in enough pure water to give 500 milliliters of solution. Let's put a decimal point after that last 0. What is the molarity of this solution? So what's given to us in this problem? Help me out. The mass of the solute, right? The mass of the solute. And what is that mass? 9.45, right? What else is given to us? The volume of the solution, right? The volume of the solution. What is that volume? 500, right? 500 with that decimal point, mills. It asks us, what's the molarity of this solution? Do we have either one of the things that we need to know to get molarity? No, so we're going to have. But we have things that we can convert to those things, right? So we know one other thing about the solute. What else do we know about it? It's what? Well, it's molecular formula, right? We know that, right? What is that? CH3OH, right? So can we use that to our advantage? So what will we use that for? To get the molecular weight. And the molecular weight will tell us what? The molar mass, right? OK, so how will we get the molecular weight from this? Look at the periodic table, right? So what do we got? We got 1C, which is 12.01. And if you wanted to do AMU, 4 grams per mol is fine. Plus, how many Hs? 4, 1.0 plus, how many O's? 0.004. Well, we've got to go to 2, 0, 4. This is the molar mass over here. And then erase all that calculation so we can use the rest of the formula. So we now know the molar mass, moles, right? Because that's what we want. OK, can I erase this stuff here? So let's go about doing this now. Take the grams, convert it to moles, right? So what are we going to put on the top? 1 mole, right? 32.04. The number of cyclics our answer is going to be 2. What's going to be up top? On the bottom, concentration is 0.590, OK? Are we ready to go with that? Any questions about how to do that? So remember, you've got to remember the stuff that we learned before. You've got to remember molar mass will convert grams to moles. You've got to remember, of course, the milliliter to leader conversion, you know, and other conversions, too.