Chapter+10 - Chapter 10 - Spontaneity, Entropy, and Free...

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Chapter 10 - Spontaneity, Entropy, and Free Energy 10.1 Spontaneous Processes 10.2 The Isothermal Expansion and Compression of an Ideal Gas 10.3 The Definition of Entropy 10.4 Entropy and Physical Changes 10.5 Entropy and the Second Law of Thermodynamics 10.6 The Effect of Temperature on Spontaneity 10.7 Free Energy 10.8 Entropy Changes in Chemical Reactions 10.9 Free Energy and Chemical Reactions 10.10 The Dependence of Free Energy on Pressure 10.11 Free Energy and Equilibrium 10.12 Free Energy and Work (skip) 10.13 Reversible and Irreversible Processes: A Summary (skip) 10.14 Adiabatic Processes (skip)
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Outline ! Spontaneity ! Number of microstates and entropy ! Definition of entropy ! Entropy changes and spontaneity
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Spontaneity ! Spontaneous process have a directionality ! Ice at room temperature melts and will not spontaneously crystallize again ! Heat flows from an object at higher temperature to a colder one ! Na and Cl 2 react explosively in the presence of small amount of water but NaCl(s) does not decompose into Na and Cl 2
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Entropy ! Based on observation, a common characteristic to spontaneous processes is an increase in ENTROPY ! This is the SECOND LAW of Thermodynamics ! S universe > 0 (spontaneous process) ! Entropy is a measure of the increase in DISORDER ! Entropy is a STATE FUNCTION ! Macroscopically, the change in entropy (at constant temperature) is defined in terms of the heat transfer (for a reversible path) divided by temperature (units of J/K) ! ! S(isothermal) = q rev /T
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Spontaneity: Molecular View ! Example: expansion of an ideal gas into a vacuum with no transfer of heat (adiabatic expansion) ! Gas expands from V/2 to V ! Probability of finding any particular molecule on one side or the other is 1/2 ! On average the molecules will be uniformly distributed between the two sides ! What is the probability of finding all of the molecules on one side? ! Spontaneity and entropy are related to the probability of the occurance of a state
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Microstates ! Say we have 4 molecules in our vessel ! What are the probabilities of finding all of the molecules on the left side? ! Probability of finding any particular molecule
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Chapter+10 - Chapter 10 - Spontaneity, Entropy, and Free...

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