 Okay, how about this one? It's observed that 4.90 kilo-cals of energy are released when a 27.6 gram sample of an unknown liquid condenses. What is the heat of vaporization of the unknown liquid in calories per gram? Okay, so we want heat of vaporization and the units are going to be calories per gram. Okay, we've got the energy, right, energy, it says is 4.90, I believe, yeah, k-cals, right, how many k-cals per, or how many calories per k-cals, 1,000, and you've got the mass, right, 27.6. So you could go back to that formula that you figured out earlier, or you could just look at these units here, say calories per gram, right, you've got grams, you've got calories, okay. The last thing you want to know is that the delta H of condensation equals the negative, or we'll do this, the negative delta H of condensation equals the delta H of vaporization. Why is that? Because we've got a liquid here that goes going that way, vaporization, right, to a gas, going this way is condensation, okay. So they're opposite of each other, those two numbers. So what you find in here is when you take, because this is how much energy is released, it says. Well, the other thing we need to know is when something says it's released, that means it's giving off energy, so it's, the energy is leaving it, right, so we've got to put a negative sign in front of that. So that's actually negative 4.90 times 10 to the third, okay, calories, because the heat is leaving it, it's being released. But this is the energy for condensation. So with our formula, what do we have, those are formula E equals delta H times M, right, from our formula last time. This delta H is not vaporization anymore, it's condensation, okay. So if we want to find the delta H of condensation, that's going to be E divided by M, right. So when we do that, right, we get E, and then when we do that, we get negative 1.8 times 10 squared cal per gram, we'll do one more cyclic, let's just do two cyclics, or three cyclics or 1.78 times 10 to the second calories per gram, right, so that's the delta H of condensation. The negative delta H of condensation equals the delta H of vaporization, like that, on a race below so I can write the answer at the bottom. So the delta H of vaporization is positive, or just.