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Homework Help: Simple distillation

  1. Oct 12, 2008 #1
    What happens to an azeotrope during simple distillation??

    for example 1-propanol + water... which I have asked here before.. but still not clear...
    but also, when you graph the boiling point-composition diagram and look at a specific composition, you read off when the liquid equilibrium is reached and when the vapour eq is reached and stuff by making sorta like staircase thing on the graph
    .. but i thought azeotrope can't be separated in simple distillation... then what's its behaviour like??
  2. jcsd
  3. Oct 12, 2008 #2


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    This question is all over the map. Please take it one step at a time.

    If you start at the azeotropic composition, you will not get any improvement in purity by simple distillation. If you start with any other composition, either the residue or the distillate (depending on whether the mixture is a positive or negative azeotrope) will get enriched while the other gradually approaches the azeotropic composition with repeated distillations.

    Make sure you know the definitions of all the underlined terms.
  4. Oct 13, 2008 #3
    i believe we started with the azotropic composition...
    well.. the only info given was the boiling temperature of 1-propanol + water....soo
    but for 70% pentanol and 30% water, what can you get out of the boiling-composition graph??
  5. Oct 14, 2008 #4


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    People may not have read your previous threads, so you need to be complete in your description here. I must admit I can not understand your query, so I'll let someone else help out with this.
  6. Oct 14, 2008 #5
    It was regarding the boiling-composition graph.
    Say we graphed a minimum boiling azeotrope's graph.
    the x-axis tells you how much of each component you have..
    say i was to read off 70% of something and 30% of the other component.
    From the y-axis I can get the boiling temperature of the liquid and the vapour.
    but when it asks you to state the behaviour of the composition (70% water 30% pentanol for ex.) what would you write?
    i know that you do the little stair thing where you read off a temperature from the liquid curve and then move horizontally to the vapour curve and stuff... and that's about all i know! lol
  7. Oct 15, 2008 #6


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  8. Oct 16, 2008 #7
    oh ok thanks.
    but when you graph temperature vs volume of distillate with a minimum boiling azeotrope... What can you conclude from it? It'd probably be a curve going up... as temp goes up, more distillate formed... how does this relate to the fact that it was an azeotrope mixture?? mind you this is simple distillation.. so nothing was separated at a higher temp. right?
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