Enthalpy of Formation

Jules Bruno
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So at this point, we have identified three ways to determine the entropy, or heat of reaction, otherwise known as Delta H of reaction. Here we have constant volume Kalorama Tree, which uses a bomb calorie meter to find the entropy of reaction or heat of reaction off combustion reactions. Then we have thermal chemical equations, which uses stoy, geometry and a balanced equation to find Delta h of reaction. Then, finally, Hess's law. If you haven't seen it yet, it uses the n tal piece of partial reactions to find Delta h of reaction for the overall reaction. Now, if the first three ways air unavailable, then we use the standard and fill appeal formation for substances to find the Delta h of reaction. We're going to say, recall that element in its standard state is given an entropy of formation off zero. So here we can use our standards standard heat of reaction formula to help us find Delta h of reaction. Here it's Delta H of reaction in its standard state. That's what this little zero means here equals the summation for the centerpiece of formation of products, minus the summation of the centerpiece of formation for reactions or broken down. In its simplest way, Delta H of reaction equals products minus react. It's so here. Delta H Little Circle on top reaction. This is the standard entropy or reaction? Heats of reaction. Yeah, in killing jewels, this Sigma side just means the summation or some up, and we'll see how that works here and equals the moles of your substance. And then here we're going to say that Delta H F with the little circle equals the standard entropy, or heat of formation for substance in killing jewels over moles or sometimes jewels over moles. Depending on what units they are, it's always gonna be killed, jewels or jewels over moles. So now that we've seen this standard heat of form of reaction formula, we're going to see how it works and use it in the next video. So click on the next video. Let's take a look at example, question