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Homework Help: Chem Lab Help

  1. Oct 30, 2007 #1
    [SOLVED] Chem Lab Help!!

    My AP chem class did an experiment where we started with 0.500 grams of copper and we ended up with 0.525 grams of copper after the experiment. The experiment consisted of us sending copper through different reactions to observe the effects of a series of reactions on the initial sample, and to also see the chemistry of a transition element. We created Cu(NO3)2, CuO, Cu(OH)2, CuSO4, and some other biproducts as well.

    the experiment calls for the measuring to be precise and that was accomplished as well as it could be with the tools given. However, the percent yield ended up being 105%, a number that is impossible, obviously something went wrong with the lab, and I was wondering if there were any special properties of Cu that might have caused this increase in final mass. My theory is that the lab procedures allowed for too much error, me and my lab partner were not the only ones to have such a high percent yield, but your thoughts would still be appreciated and very helpful. Thanks
  2. jcsd
  3. Oct 30, 2007 #2
    that is a great lab.

    think about how you isolated/recovered the copper. How might you have gained mass at the end? Copper is quite sensitive to oxidation when it is heated.....

    (I have seen 130% yields! :D )
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