CHE-2211 Chapter Notes - Chapter 22: Reagent, Sulfuric Acid
6 May 2019
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Hess"s law allows us to find the enthalpy of a "problem" reaction from other reactions that are given to us as data. If a series of reactants react to give a series of products, the heat of reaction released or absorbed is independent of whether the reaction is carried out in one, two or more stages. Therefore, if you can get from some reactants to a given product from a single reaction (the. "problem" reaction) or from several (the "data" reactions), the enthalpy put into play must be the same. Hess"s law is based on the fact that enthalpy is a function of state, and therefore its value does not depend on the path followed to arrive from some items given to the corresponding products. Your enthalpy will change sign: similarly, if in a reaction "data" a substance is as a product and in the reaction "problem" is as a reactive, we must turn around the reaction "data".
