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Redox Relapse

  1. May 18, 2005 #1
    We need to know what the products of KI + H2O in ionic form.
     
  2. jcsd
  3. May 18, 2005 #2

    dextercioby

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    The reaction should be

    [tex] 2KI+H_{2}O\rightleftharpoons K_{2}O+2HI [/tex]

    which in ionic form

    [tex] 2K^{+}+2I^{-}+H^{+}+OH^{-}\rightleftharpoons 2K^{+}+O^{2-}+2H^{+}+2I^{-} [/tex]

    I don't see any redox here...

    Daniel.
     
  4. May 18, 2005 #3
    THe labis on oxidation reduction. It says that ppt turns pink in the presence of hyrdroxide ions and the starch will turn black/blue in the presence of molecular iodine. We figured that this meant that in the equation that this meant in the products their will be a hydroxide ions and an I molecule. We thought that the answer you gave us was right but our teacher said that we were closer when we showed him KI + H2O--> OH + K + I2 + H
     
  5. May 18, 2005 #4

    dextercioby

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    Yes,i didn't think of that option.There it is.Can u find the coefficients by accomplishing the electron transfer ?

    [tex] aK^{+}+bI^{-}+cH^{+}+dOH^{-}\rightleftharpoons eK^{+}+fOH^{-}+gI_{2}+h H_{2}\uparrow [/tex]

    Daniel.
     
  6. May 18, 2005 #5
    yeah we should be able to, um what are the a,b,c,d,e,f,g for?
     
  7. May 18, 2005 #6

    dextercioby

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    Coefficents,like 1,2,1/2,3/2,3.

    So who's getting oxidated and who's getting reduced...?

    Daniel.
     
  8. May 18, 2005 #7
    umm I havent done it yet;P
     
  9. May 18, 2005 #8

    dextercioby

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    It's not funny.If u haven't done redox reactions in school,why do you bother with this problem...?:rolleyes:

    Daniel.
     
  10. May 18, 2005 #9
    Me thinks something is a miss here. Was it hydroxide or peroxide ?
     
  11. May 18, 2005 #10
    it was hydroxide
     
  12. May 19, 2005 #11
    OK what is ppt ?
     
  13. May 19, 2005 #12

    Borek

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  14. May 22, 2005 #13
    the ppt is phenalthailene...and the reaction is K + I + H2O --> KOH + I + H
     
  15. May 23, 2005 #14

    GCT

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    Alright, I would imagine that this is a simple dissociation reaction, [tex]KI_{(s)}+H_2O \rightarrow K^{+}_{(aq)}+I^{-}_{(aq)} [/tex]

    The starch test will not work without molecular iodide however, I2. You'll need both I2 and I-, for the iodine complex involving I3-.
     
  16. May 24, 2005 #15
    OK I'm highly dyslexic, but did you mean phenolphthalein ? There still is something a miss here (like what would oxidize the I-).
     
  17. May 24, 2005 #16

    GCT

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    potassium reacts with water??? Never actually encountered this before, I though it would be a spectator ion. I've read about this and it seems that KI is dissolved in water to provide I-, subsequently I2 is added to form I3-, which can form complexes with starch conterparts to form a colored solution.

    I'm somewhat sensitive about the way some high schools deal with redox reactions as at times they are completely misleading and inaccurate. I've had a post in my forum a couple of months ago regarding a high school chemistry competition of which one of the answers provided turned out to be completely inaccurate. I couple of students decided to seek help online for references and quotes.
     
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