 Okay, guys, so let's use Hess's law to figure out the heat of the reaction down here that we don't know, even though we know the heats of these two reactions, okay? So remember, since delta H is a state function, we can use these two reactions to figure out the other reaction. What we need to remember is the additive properties of these equations are similar to mathematical equations, okay? So what you want to do in this instance is to make the things on the reactant side equal to the things that are down here. Make things on the product side equal to the things that are down here. But if something is presented on both the reactant side and the product side and the reactant side, that thing will cancel out, okay? So if we look here, right, we've got one sulfur on the reactant side, and we've got two sulfurs down here that we need, right? We've got three oxygens down here, but only two oxygen molecules here, okay? So if we, hopefully you guys see that if we multiply the top reaction by two, right, we will get two sulfurs here and two plus one oxygens is three oxygens down here. Is everybody okay with that? Okay, so let's do that. So when we multiply the reactions, just like my mathematical one, we have to multiply it all the way through, okay? So maybe I'll do it with a different color. So we've got now two S solid, so we multiply it by two, plus two O2 gas goes to two SO2 gas, okay? And that gives us a new delta H1, okay? Because remember, this is part of the reaction equation two. So we've got to multiply this by two as well, right? So when we do that, it equals negative 593.6 kilogens, okay? So we effectively don't have this reaction anymore. We're looking at these two reactions. So now hopefully what we can see is, yes, we've got our two sulfurs, we've got our three oxygens down, but we've got some SO2s here that aren't present here and some SO2s here that aren't present here, okay? But if they're on both sides of the reaction, they'll cancel each other out, okay? Just like a mathematical equation, okay? So since there's two here and two there, they cancel each other out quantitatively like that. So now hopefully you guys can see is if we add this to this, we get this, and if we add this to this, we get this. You guys see that? Okay? So since that's the case, remember, Hess's law is delta H of the reaction, hopefully I have enough room and you guys can see this on the video, is delta H1 plus delta H2, delta H1, here let's just do it up on the top here, delta H1 is negative 593.6 kilojoules plus negative 198.4 kilojoules. So that should give us the heat of reaction to 0.0 kilojoules is the heat of reaction. Do you guys get that? Are there any questions on Hess's law, okay? Or at least this particular question of Hess's law? We'll do some more in a bit.