 Okay, so let's do this one. It says, what is the molarity of a nitric acid solution if 68.5 mils is needed to react with 25 mils of a 0.15 molar potassium hydroxide solution? Okay, so you need to know quite a few things. Remember what we were talking about is we need to set up that chemical reaction or that chemical equation before we do anything, okay? So what hopefully you recall is an acid-base reaction is the transfer of an H plus to a base, right? I don't know, but in this case, it's OH minus. So our reaction equation is going to be HNO3. All of these are going to be A plus. What is the KOH? Those two. So hopefully you can see this acid is what we call a monoprodic acid. It's only got one H plus here. And this only has one hydroxide. Remember, we want to make water. So that's just going to transfer to that. And we're going to have the other. So this is going to be, remember, a double displacement reaction, or a double replacement reaction. So we're going to have water. And the other thing should be potassium nitrate, right? Okay, so potassium nitrate. And you guys should be able to do, so this is what's called the molecular equation of the acid-base reaction. You should be able to do the metionic and the total ionic equations here. Know what the spectator ions and all that. This problem doesn't deal with that at all. Let's go about writing the stuff down now that it tells us. So it says, what is the molarity of nitric acid? So that's what we're looking for. 68.5 mills, so the volume of nitric acid, 0.5 mills, is needed to react with the volume of KOH, 0.150 molar. Remember, this molar is moles per liter. So that kind of helps you out. So I'm going to change it. So moles of KOH, 1 liter of solution. So remember, this here is milliliters of solution. Is everybody OK with that? So let's convert this to liter. So we can use this conversion factor to figure out how many moles of KOH we have in 25 mills of the solution. Is everybody OK with what I'm doing so far? If you're not, tell me. And this, if you want to. You can use this one here, all right, to figure out how many moles. So remember, molarity, so now we're not figuring out volume anymore. We're figuring out the number of moles of KOH. Is everybody OK with that? So we'll use this molarity. Say 1 liter of solution is 0.150 moles of KOH. Number of moles of nitric acid that we have from this, too? We could, right? Because we've got this chemical equation here. Is everybody OK with that? So let's just do that. What's the ratio? 1 to 1. Very good. 1 mole, 1 mole, Hn of 3. So what are we trying to figure out? The molarity, right, of yours here. We're just going to have to convert it, right? So let's go ahead and figure out the number of moles of nitric acid that we've got. So this is no longer this, right? It's now the number of moles of Hn of 3 divided by 1,000 times 1, of course. And of course, you could convert this to scientific notation if you wanted to, but I'm just going to leave it like this for right now. And we'll do that at the end if we need to. So notice what we have here now. We have the moles of nitric acid, right? And we have the volume of nitric acid. Should we be able to find the molarity of that from that? OK. Why? Because molarity of nitric acid is going to be what, the number of moles. I really want to be dyslexic today of nitric acid over the volume in liters of nitric acid, right? And we've got that. And we've got that, so let's just plug and show it. So 0.00375 mole of, if you want to say, Hn of 3 divided by 0.0685 liters of solution. And that's going to equal 0.05. And how many 6 bigs are we going to have? So 3, depending. So 0.0547 molar of 3. So you can leave it like that. Or of course, you can put 5.47 times 10 to the negative 2 molar Hn of 3. That seems like a reasonable molarity to me. OK? Is everybody OK with how we did that? Remember, step, step, step, step. If you're not doing it every step and converting a unit, or if you're putting no units in there, you're probably getting confused and not understanding why we're doing it. OK, are there any questions about this before I kill it? Before I kill it? OK.