 So this one tells us what is the molarity of a nitric acid solution if 68.5 mils is needed to react with 28.0 mils of a 0.150 molar koH or potassium hydroxide solution. So the first thing I guess I always like to remember especially if I'm in your situation is molarity here means moles per liter. So I like to write that out moles per liter and that's a potassium hydroxide. So let's just put that to keep our place koH koH. Up here we have milliliters of koH. Up here we have mills of nitric acid. So hopefully you notice we've got milliliters here and liters down here. So we're probably going to want to convert to liters. So I'm going to do that straight away. So 1,000 mils of koH solution equals 1 liter of koH. So we know how many liters of koH we have. And we know how many moles per liter of koH we have. So we should be able to figure out how many moles is in this volume of koH. Does everybody understand what I'm saying? We should be able to figure that out. How do I do that? Multiply by 0.0250 liters of koH. So when I do that, liters, cancel with liters there. You guys see that? And I get some number that we're about to calculate. 0.15 times 0.025. 3.75 times 10 to the negative 3 moles koH. Right? So we know the number of moles of koH. Is everybody okay with that? So from there we should be able to figure out the number of moles of nitric acid. Right? HNO3. How would we do that? Well, good job guys. We would look at the chemical equation and get that information from there. Okay? So what do we know about the moldable ratio? 1 to 1. Right? 1 to 1. 1 mole koH. That should cancel out of that. So remember, we're looking for the polarity of nitric acid. We want to get polarity, we need volume in liters. So that'll give us the volume in liters. 0.0685 liters nitric acid. Well, we didn't finish this calculation, but this is 3.75 times 10 to the negative 3 moles of nitric acid. So we've got the moles of nitric acid and we've got the liters of nitric acid. Shouldn't we be able to calculate the concentration? Yeah. Right? So the concentration, the molar concentration of nitric acid is going to be the number of moles. 3.75 times 10 to the negative 3 moles of nitric acid divided by 0.0685 liters of nitric acid. And I got 0.05, how many? 3. So 547 molar nitric acid. Okay. So hopefully you guys can do that. Are there any questions on anything that we've done here? Not to use the M1V1. So it's a good question, it was asked before. So why do I not use M1V1 in this particular equation? First of all, it's a different problem, M1V1. Okay? So in this one, we're given volume and molarity of KOH, right? And we're looking for the molarity of something else. Okay? And the M1V1s, we're just diluting or concentrating a solution of like KOH, right? It gives us KOH and wants us to know the final concentration of KOH. Okay? In fact, like I was saying, if you use M1V1 on this one, you'll actually get the right answer, but the process that you're doing is wrong, okay? And I'll prove it to you by doing another problem like this, okay? Another acid-base problem like this with the same numbers, but with different things up here that we're reacting. And if we could use M1V1, we should give this every time, right? But we won't in the next one. So it's imperative that you use this process whenever you're doing a titration, not M1V1. Does that make sense? Questions, questions? This is a good question, okay?