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Homework Help: Which valence state do I use?

  1. Sep 28, 2008 #1
    1. The problem statement, all variables and given/known data
    I have to write a net ionic equation for Cr and silver nitrate, but I am confused on which valence state to use, since Cr has multiple valence states ie +2, +3 and + 6.


    2. The attempt at a solution
    If I use the valence state of +2 I end up with:
    Cr(s) + 2 Ag+(aq) = 2 Ag (s) + Cr2+(aq)

    But if I use +3 I end up with:
    Cr(s) + 3Ag+(aq) -> 3Ag(s) + Cr3+(aq)

    So which one do I use? and is there a rule to follow?

    Thanks.
     
  2. jcsd
  3. Sep 28, 2008 #2

    Borek

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    Staff: Mentor

    In general you should compare potentials of half reactions. In this case go for Cr3+.
     
  4. Sep 28, 2008 #3
    Thanks borek. :)

    Another quick question. Neither of these reactions would occur correct?

    1.Au + HCl
    No reaction since Au is below H2 in the activity series.

    2.Ni + Ca(C2H3O2)2 (Ca acetate)
    No reaction since Ni is below Ca in the activity series.
     
  5. Sep 28, 2008 #4

    Borek

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    Staff: Mentor

    2xOK
     
  6. Sep 28, 2008 #5
    Thanks.
     
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