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Ethanol and water mixing

  1. Jan 19, 2010 #1
    1. The problem statement, all variables and given/known data
    when ethanol an dwater are mixed, is randomness increased or decreased


    2. Relevant equations



    3. The attempt at a solution
    Since these are miscible, I 'm equating that with 'comfortable' as a mixture and the 'comfort' being like a smaller amount of entropy than when the two are together but not mixed
    However, I'm uncertain about this conclusion that I've drawn as an answer. The fact that heat is released in the process suggests to me a minimum energy favours the mixed versus the solution of one in the other. Do these ideas sound reasonable?
     
  2. jcsd
  3. Jan 19, 2010 #2
    ethanol is polar like water, which can form hydrogen bonds. I'm thinking that randomness should be decreased because there's some stability of the mixture.
     
  4. Jan 20, 2010 #3
    Yes that's what I thought. Thanks for the guidance.
     
  5. Jan 21, 2010 #4
    Would this mixture, the state of decreased randomness, constitute a state of minimum energy or maximum energy. I'm thinking this because doesn't increased randomness always go along with minimum energy?
     
  6. Jan 21, 2010 #5
    I know the answer (mixture is always more random, meaning higher entropy, than two pure substances) but not how to explain it. Maybe the explanation is that you can't separate a mixture without spending energy.
    Another thought- visualize baseballs (H2O molecules) and footballs (C2H5OH), in two separate bins. MIxing them up requires very little wok; and they can be mixed in thousands of ways (high disorder). Separating them back again to the bins takes a lot of work, and they can be arranged in fewer ways (low disorder).
     
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