ch.16-17test3 - Chapter 16 Spontaneity Entropy and Free...

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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.
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