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Extraction question

  1. Sep 26, 2005 #1
    Suppose a reaction mixture, when diluted with water, afforded 300mL of an aqueous solution of 30 g of the reaction product malonitrile,CH2(CN)2 which is to be isolated by extraction with ether. The solution of malonitrile in ether at room temperature is 20.0 g per 100 mL, and in water is 13.3 g per 100 mL. What weight of malonitrile would be recovered by extraction with (a) three 100 mL portions of ether; (b) one 300-mL portion of ether. Suggestion: For each extraction let x equal the weight extracted into the ether layer. In case (a) the concentration in the ether layer is x/100, and in the water layer is (30-x)/300; the ratio of the quantities is equal to k = 20/13.3.
     
  2. jcsd
  3. Sep 26, 2005 #2
    any ideas? anyone?
     
  4. Sep 27, 2005 #3

    GCT

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    what's the problem? You've got most of what you need right here.

     
  5. Sep 27, 2005 #4
    Is this right?

    Well, is this right?


    1) k = 20/13.3 = 1.5
    x/30-x = .50
    x = .5(30-x)
    1.5x = 15
    x = 10g in ether layer
    30 – x = 20g in water layer

    x = .5(20 – x)
    x = 10 -.5x
    1.5x = 10
    x = 6.67
    20 – x = 13.33


    x/13.33 – x =.50
    x = .50(13.33 – x)
    x = 6.67 - .5x
    x = 4.44
    13.33 – 4.44 = 8.89

    a) 21.1g = three 100-mL portions of ether

    x/30-x =1.5
    x=1.5(30-x)
    x =45-1.5x
    2.5x/2.5 =45/2.5
    x = 18.0

    b) 18.0 g = one 300-mL extraction of ether
     
  6. Sep 28, 2005 #5

    GCT

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    yep everything seems correct
     
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