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Help with chem lab

  1. May 3, 2007 #1
    I'm very confused with an electrochemistry lab. For the lab, we used Al+3, Cu+2, Fe+3, Zn+2, and KNO3. The setup was wells with all of the solutions in them. We soaked a piece of paper(filter paper) in KNO3 for the reactions, then used the paper as a salt bridge between the solutions of the ions for all combinations(i.e. Cu+2 with Fe+3, Fe+3 with Zn+2 etc.). What I'm confused with is how to write the reactions as both cells have positive ions in them, making them both reduction reactions, unless I'm missing something horribly wrong. Can someone help me? I have no clue what the oxidation reactions are. This is what I have so far:
    [tex]
    \subsection{\ce{Al^{+3}} and \ce{Cu^{+2}}}
    \paragraph{\ce{Cu^{+2}} half reaction}
    \ce{Cu^{+2} +2e^{-} -> Cu} .34V
    \paragraph{\ce{Al^{+3}} half reaction}
    \ce{Al^{+3} + 3e^{-} -> Al} -1.66V
    \subsection{\ce{Cu^{+2}} and \ce{Fe^{+3}}}
    \paragraph{\ce{Cu^{+2}} half reaction}
    \ce{Cu^{+2} +2e^{-} -> Cu} .34V
    \paragraph{\ce{Fe^{+3}} half reaction}
    \ce{Fe^{+3} + e^{-} -> Fe^{+2}} .77V
    \subsection{\ce{Fe^{+3}} and \ce{Zn^{+2}}}
    \paragraph{\ce{Fe^{+3}} half reaction}
    \ce{Fe^{+3} + e^{-} -> Fe^{+2}} .77V
    \paragraph{\ce{Zn^{+2}} half reaction}
    \ce{Zn^{+2} + 2e^{-} -> Zn} -.76V
    \subsection{\ce{Al^{+3}} and \ce{Fe^{+3}}}
    \paragraph{\ce{Al^{+3}} half reaction}
    \ce{Al^{+3} + 3e^{-} -> Al} -1.66V
    \paragraph{\ce{Fe^{+3}} half reaction}
    \ce{Fe^{+3} + e^{-} -> Fe^{+2}} .77V
    \subsection{\ce{Al^{+3}} and \ce{Zn^{+2}}}
    \paragraph{\ce{Al^{+3}} half reaction}
    \ce{Al^{+3} + 3e^{-} -> Al} -1.66V
    \paragraph{\ce{Zn^{+2}} half reaction}
    \ce{Zn^{+2} + 2e^{-} -> Zn} -.76V
    \subsection{\ce{Cu^{+2}} and \ce{Zn^{+2}}}
    \paragraph{\ce{Cu^{+2}} half reaction}
    \ce{Cu^{+2} +2e^{-} -> Cu} .34V
    \paragraph{\ce{Zn^{+2}} half reaction}
    \ce{Zn^{+2} + 2e^{-} -> Zn} -.76V
    [/tex]
     
  2. jcsd
  3. May 4, 2007 #2

    symbolipoint

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    Homework Helper
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    Gold Member

    You seem to have not stated what counter half cell was used for each have reaction which you listed. You would not expect much with just a half cell plus a salt bridge. Did you have reactions between the Nitrate and a metal ion?
     
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