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Identifying Spectator Ions

  1. Dec 11, 2009 #1
    1. The problem statement, all variables and given/known data

    2KMnO4 (aq) + 10FeSO4 + 8H2SO4 -->

    K2SO4 (aq) + 2MnO4 (aq) + 5Fe2SO4 (aq) + 8H2O (aq)

    2. Relevant equations

    Spectator ions don't participate in the reaction.

    3. The attempt at a solution

    What gives? Is my professor bent on making our lives miserable? The answer for the above is: the spectator ions are K+ and SO4.

    I understand spectator ions don't participate in the reaction... but what's so divinely different between K+ and SO4 that isn't happening in the other ions? There are two Sulfate ions in the productsby the way which adds to my confusion...
  2. jcsd
  3. Dec 11, 2009 #2


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    Staff: Mentor

    First of all - write everything in dissociated form. It is not called "net ionic" for fun :wink:

  4. Dec 12, 2009 #3
    Here are the spectator ions:

    2K+ + 2MnO4- + 10 Fe2+ + 10SO42-


    2K+ + SO42- + 2MnO4 + 10Fe1+ + 5SO42- + 8H2O

    Hmm. Interesting that I found the net ionic equation. The only ions I see that are the same are the K+ and SO42- ions. The manganate ion, 2MnO4- doesn't count because the product MnO4 is not an ion correct?

    And same for the ion right? It's not a spectator ion because one is of +2 charge and the other of +1 charge?
  5. Dec 12, 2009 #4


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    Staff: Mentor

    Where did you get the original equation from? I must admit I have not taken a closer look before, now that I did rest of the hair on my head rasied up.

    But your analysis seems to be OK, only K+ and SO42- remain unchanged after the reaction.

  6. Dec 12, 2009 #5
    The original equation was pulled from an old exam of my undergrad chemistry professor. It was a little weird, so it was worth discussing.

    Thank you for your analysis and general helpfulness Borek. This question was a bit weird!
  7. Dec 12, 2009 #6


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    Staff: Mentor

    To be honest I hate questions that are based on nonexisting chemistry, they only create confusion.

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