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Homework Help: Reasons why % yield would be so low, synthesis of zinc iodide

  1. Feb 16, 2010 #1
    1. The problem statement, all variables and given/known data

    In my Chem lab we synthesized zinc iodide.

    To 1g granulated zinc, 2ml distilled water and 4 drops of 2 M acetic acid was added. Then 1g of iodide. The mixture was agitated and several minutes later the reaction completed.

    There was some excess zinc, so we set up a gravity filter and poured the contents of the test tube on the filter paper. The zinc iodide dripped through the filter into an evaporating dish. We dried and weighed the excess zinc. The percent of zinc recovered was normal, about 94%. I know where we could have lost some excess zinc.

    On a hotplate we dried the zinc iodide, removing the water by evaporation. There was some popping and splattering of the zinc iodide crystals so I know that we could have lost a bit of product there.

    My main question is where else could we have lost some of the product, zinc iodide? Our percent yield was 39.7%. This might be normal, I'm not sure.

    Can you suggest some other reasons why our percent yield was so low? My calculations are correct for the theoretical yield and actual.

    [tex]\frac{.5g}{1.258g}[/tex] = 39.7%
     
  2. jcsd
  3. Feb 17, 2010 #2

    chemisttree

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    How hot did you heat the zinc iodide?
     
  4. Feb 17, 2010 #3
    medium to medium-low, to prevent splattering
     
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