 So let's do this one and after that harder one it seems like this one's much easier So we'll read the question it says the industrial decreasing solvent dimethyl Dichloromethane or methylene chloride is prepared from Methane by reaction with chlorine and they give this reaction Methane plus two fluorines goes to the Dichloromethane plus two HCl And they're wondering well, what's the heat of that reaction and they give us these two reactions here And they give us the heats of the reactions. Okay, so in this case We just need to make sure That all the things that are here are represented here and all the things that are here are represented here If they're not then we're going to have to do some rearranging of these equations either turn them around or multiplying by two or one Okay, so let's just first go through it cancel out the things that are on both sides. Okay with the equation So we see we have Methane here one methane and we have one methane here two chlorines here and two chlorines here So that's good, right, but we have this chloromethane here. That's not present here Okay, so if we look over here, we've got the two HCl's. That's good Dichloromethane. That's good But we've got that chloromethane here. Okay, so what can we do since they're on? Yeah, since they're on one's on one side and one's on the other side They can cancel each other out just like a mathematical equation like that So when we do that, of course, this this is the additive sum of these two lines This is the additive sum of these two lines So this must be the additive sum of these two lines here Okay, so let's go ahead and add those together and on our calculator so 93 98.3 plus minus 104 okay, and 104.0 that is and if we're going to the right amount of sick things This is going to be negative two oh two point three Kilogens, so any question on this one? I know it's pretty straightforward after the ones that we have already done so I Didn't realize it was going to be that way so guys are way past this but any questions before I kill it