Chapter 9 Notes - Test 3

Chapter 9 Notes - Test 3 - Chapter 9 Chemical Equilibria...

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Chapter 9 – Chemical Equilibria Reactions at equilibrium Chemical equilibrium - the stage in a chemical reaction when there is no further tendency for the composting of the reaction mixture (the concentrations or partial pressures of the reactants and products) to change. Like physical equilibria, all chemical equilibrium are dynamic equilibria, with the forward and reverse reactions occurring at the same rate. Reactants are being formed as fast as they are consumed. As a result to dynamic equilibria, the composition of a mixture remains constant. Criteria that identify a dynamic chemical equilibrium: 1. The forward and reverse reactions are both taking place. 2. They are doing so at equal rates (so there is no net change). Dynamic equilibria respond to changes in temperature and pressure, and the addition of even a small amount of additional reagent can result in a change in overall composition. A reaction that is not taking place (a mixture of hydrogen and oxygen at room temperature and pressure) does not respond to small changes in the conditions. 9.1 The reversibility of Reactions When the reaction does not proceed to completion, but seems to stop and no more product forms, the reaction has reached equilibrium 9.2 Equilibrium and the Law of Mass Action The same value of K can be obtained no matter what the initial composition of the reaction mixture. K is the equilibrium constant for the reaction, and is characteristic of the composition of the reaction mixture at equilibrium and at given temperature. Law of Mass Action – at equilibrium, the compositions of the reactions mixture can be expressed in terms of an equilibrium constant where, for any reaction between gasses that can be treated as ideal K = {partial pressures of products/partial pressures of reactants} equilibrium with each partial pressure raised to a
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This note was uploaded on 04/07/2008 for the course CHM 115 taught by Professor Lab during the Spring '08 term at Wilkes.

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Chapter 9 Notes - Test 3 - Chapter 9 Chemical Equilibria...

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