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Ethanol - salt precipitation

  1. Mar 11, 2012 #1
    1. The problem statement, all variables and given/known data


    what is the purpose of adding ethanol in step 5 in the following description?

    http://www.creative-chemistry.org.uk...s/N-ch5-08.pdf [Broken]
    2. Relevant equations


    3. The attempt at a solution
    Does adding ethanol make the liquid phase (which is now a homogenous mixture) less polar because ethanol is slighly hydrophobic hence the salt is less soluble so precipitates out?
     
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Mar 11, 2012 #2

    Borek

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    Staff: Mentor

    Link is broken.

    But your explanation is more or less what could be expected.
     
  4. Mar 11, 2012 #3
  5. Mar 11, 2012 #4

    Borek

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    Staff: Mentor

    I don't think calling ethanol hydrophobic is the best approach. It has a lower dielectric constant and because of its size it is not as effective at solvation, so it doesn't isolate ions as effectively as water does.
     
  6. Mar 11, 2012 #5
    would it please be possible then to give me an A2 level answer (i don't know about dielectric constant) that would gain 1 or 2 marks?

    thanks
     
  7. Mar 11, 2012 #6
    would the following be better:

    "the homogeneous mixture of ethanol and water is less polar that water alone so the salt is less soluble and hence precipitates out
     
  8. Mar 11, 2012 #7

    Borek

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    Staff: Mentor

    Sounds good to me.
     
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