 So since we just did the lecture on partition coefficient, let's try problem using that. I've just gone ahead and written down all the useful information that we'll be able to pull out of this problem. So we won't have to watch me do it on the video. But anyway, I'll read it to you. It says, consider the situation where 15.5 grams of caffeine is added to a mixture of 100 mils of water and 100 mils of chloroform. Since water and chloroform are essentially immiscible, two layers will form. Given that caffeine is soluble in both water and chloroform, 1.5 grams per 100 mils and 14.0 grams per 100 mils at 25 degrees Celsius respectively, it will be partitioned between the two layers. So the question says, what is the value for the partition coefficient for caffeine when it's partitioned between water and chloroform at 25 degrees Celsius? So remember, what's happening here? So let's draw our separatory funnel. So just to get a kind of picture of what we might see in the lab. So there's your separatory funnel. It's on a ring stand, a sphere, whatever. Thing is here. So separatory funnel, when you put your water and your chloroform in, you're going to have two layers. And you'll see this rather distinctly. So since chloroforms were dense, it'll be on the bottom. And what you'll find is that you took all the chloroform out and evaporated it off. You find some amount of caffeine in there. And then you took all the water out. But it wouldn't be the total amount that you put in 15.5 grams. And you took all the water out, then you find the rest of it. So that's what's happening. It's partitioning in between the two layers. So what do we know about the partition coefficient? We know kp concentration of the solute, solvent 2, divided by the concentration of the solute. Mills will cancel if we think it's mills of solvent. And that'll give you can do this. 100 divided by 100 will cancel. And that'll give us 1. So 14 divided by 1.5, 9.3. So that's the kp for caffeine. Partition between water don't cancel here, which they will in all of these partition coefficient problems that I'm giving you. But even if they don't in coefficient questions, you're going to have no units. Try another one in a second.