Hess's Law

by Jules Bruno
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many reactions cannot be carried out in a single step, but instead require multiple steps to get to the final product. We're gonna say Hess's law states that the entropy of reaction often overall reaction is the sum of the entropy is the standard. Entropy values off these multiple steps. So here we have a partial reaction one and a partial reaction to By combining them together, they helped to give me my overall reaction down here. Now what we do is this Zenon die Fluoride is reacting so it comes down. Then we're gonna say here that this flooring, which is a solid I'm not not solid. A product cancels out with one of these florins, which is a reactant, remember, they can't exist on both sides. OK, this causes an imbalance. These air called reaction intermediates and they will cancel one another out. So this cancels out with one of these leaving us with one behind this Zen in here is a product. And this one here is a reactant again can exist is both. There's one and one on each, so they both cancel out each other entirely. What's left behind comes down. So this f two comes down to give me this reactant, and then this Zenon try. Florida comes down to give me this final product to find the overall entropy of reaction. For this overall reaction, you add up each of these partial standard entropy values, So when you add 1 23 and you subtracted, subtract 2 62. That's how we come up with this new Delta h of reaction. That's a negative 1. 39 Kill a Jules. This, in essence, is what Hess's law tries to do. It takes partial reactions and from them helps us to determine the overall reaction and associated with it in overall entropy of reaction.