Entropy

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Entropy free energy (Ch_18) but not 18.6

• Or, why do chemical reactions occur?

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Definitions Chemical

• A substance that
• 1) An organic chemist turns into a foul odor
• 2) an analytical chemist turns into a procedure
• 3) a physical chemist turns into a straight line
• 4) a biochemist turns into a helix
• 5) a chemical engineer turns into a profit.

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Review

• In chapter 6 we discussed the convertibility of
  energy from 1 form to another (the 1st law). Now
  lets look at the 2nd law

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The 2nd Law

• The entropy of the universe increases in a
  spontaneous process and remains unchanged in an
  equilibrium process
• For a spontaneous process
• For an equilibrium process

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This stuff is related

• We learned about enthalpy is a useful measure of
  internal energy plus pressure volume
• Now we see that entropy is a measure of disorder
• Now we tie it all together with Gibbs free
  energy- the energy available to do work

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Gibbs Free Energy

• GH-TS
• This is another state function
• At constant temperature

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Exam Questions

• Understand order in gasses, liquids and solids
  and be able to arrange various compounds in
  increasing entropy order
• Calculate ?S given S? for reacting and product
  species
• Calculate ?G and be able to predict if a reaction
  will occur, if heat must be added, what
  temperature must be reached

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More Exam Questions

• Be able to predict whether entropy is increasing
  in a series of different reactions
• Calculate entropy of a specific reaction given
  values of S0 for each reactant
• Calculate

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Philosophy

• There is a strange property relating to entropy.
• If we observe a very probable configuration in
  the past, we continue to observe a very probable
  configuration!
• But if we arrange the system in a very improbable
  configuration in the past, it rapidly adjusts
  itself to a probable one.
• Think of a glass of water with one drop of ink in
  it carefully placed so it just floats there, and
  another glass with the same amount of ink
  thoroughly mixed.
• Let the glass with the visible drop sit for a
  day.
• Look at both glasses, measure them with
  everything youve got, you cannot tell the
  difference.
• Reverse time for a day. In one glass the drop
  reappears, in the other, absolutely nothing
  happens!
• Entropy gives us the real arrow of time like
  nothing else.
• Whoa!

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Or maybe its just a rounding error and we are a
big computer model on a machine run by someone a
lot smarter then we. Albert Migliori, after a
statistical check of the Poisson ratio of the
corks in many wine bottles.

• The question of the physical foundations of the
  law of monotonic increase in entropy thus remains
  open it may be of cosmological origin and
  related to the general problem of initial
  conditions in cosmology the violation of
  symmetry under time reversal in some weak
  interactions between elementary particles may
  play some part. The answers to such questions may
  be achieved only in the course of further
  synthesis of physical theories.
• Statistical Physics by L.D. Landau and
  E.M.Lifshitz