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Unformatted text preview: Chapter 16 Spontaneity, Entropy, and Free Energy 16.1-Spontaneous Processes and Entropy ⋆ A process is said to be spontaneous if it occurs without outside intervention. ⋆ Thermodynamics allows us to know the direction of a process and whether or not it is likely to occur but tells us nothing about the rate ⋆ The rate of a reaction depends on activation energy, temperature, concentration, and possibly a catalyst ⋆ Chemical Kinetics focuses on the pathway between reactants and products The driving force for a spontaneous process is an increase in the entropy (S) of the universe. ⋆ Entropy (S) can be viewed as a measure of molecular randomness or disorder. The natural tendency of the universe is to go from order to disorder (low entropy to high entropy). ⋆ Positional Probability is probability that depends on the number of configurations in space that yield a particular state. S solid < S liquid < S gas ⋆ Entropy increases when solutions are formed because the total volume that each substance can use is now increased and therefore greater disorder and positional probability can be achieved. ⋆ The First Law of Thermodynamics is: Energy cannot be created nor destroyed; all energy in the universe is constant. 16.2-Entropy and the Second Law of Thermodynamics ⋆ The Second Law of Thermodynamics is: In any spontaneous process there is always an increase in the entropy of the universe. We can represent the change in the entropy of the universe as S universe = S system + s surroundings ⋆ If S is positive the entropy of the universe increases and the process is spontaneous in the direction written. If S is negative the process is spontaneous in the opposite direction. If S is 0 the process has no tendency to occur and the system is in equilibrium. 16.3 The Effect of Temperature on Spontaneity ⋆ Entropy changes in the surroundings are determined primarily by the flow of energy into or out of the system as heat. When heat flows out of a system and into the surroundings (exothermic processes) the S is positive. processes) the S is positive....
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This note was uploaded on 03/09/2008 for the course CHEM 1B taught by Professor Hagopian during the Spring '06 term at Irvine Valley College.
- Spring '06