CHEM 204 Lecture Notes - Vapor Pressure, Pressure Cooking, Molality
15 Jul 2013
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Recall: we use gibbs energy to predict equilibria of chemical reactions. A reaction mixture will keep adjusting until gibbs is minimized. A negative g is always spontaneous, and a positive g is never spontaneous. Rg = n g (products) n g (reactants) By calculating the total fg for a system of reactants and products at all possible combinations, we get this prediction curve: spontaneous reactions. The lowest gibbs energy occurs slightly to the left, so there is always a tendency to mix with some of the reactant: non spontaneous reactions: The reaction shouldn"t go forward, but it does a little bit because of the entropy of mixing makes the lowest gibbs energy slightly to right. *if you remove the products as they are made, you can drive the reaction forward. Our body does this for non-spontaneous reactions: perfect equilibrium: The minimum of the total gibbs lies in the middle between the pure reactants and pure products.
