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Homework Help: In desperate need of help!

  1. May 17, 2006 #1
    Help me! Redox help, product predictions

    I have a lab that we have to get a perfect score on to pass the class, and I'm so overwhelmed and confused right now I could really use some major help.

    Basically we were given the names of 9 mixes, and we have to predict whether or not they will have a ppt, and if not then we have to move onto redox, see who wants electrons, who's losing them, and then write the half reactions, balance, and then find the overall Eo(volts).

    So... the main ones I have trouble with are (and what I have started):

    Magnesium nitrate and Sodium Sulfate
    MnNO3 + Na2SO4 --> NaNO3 + MnSO4 ??

    Potassium permanganate and 1.0 molar HCl
    KMnO4 + 2HCl --> Cl2 + K + MnO4 + 2H ??

    Potassium iodide and iron III chloride and 1 ml of petroleum ether
    KI + FeCl3 --> Fe + I + KCl ??

    Potassium bromide and iron III chloride and 1 ml of petroleum ether
    KBr + FeCl3 --> Fe + Br + KCl ??

    and Iron II sulfate (acidified with 3 drops of 6 molar sulfuric acid) and .01 molar potassium permanganate
    FeSO4 + KMnO4 --> i think this neutralizes.. but i dont know

    I am so swamped with homework, it would be extremely appreicated if someone could even point me in the right direction, thank you!
    Last edited: May 17, 2006
  2. jcsd
  3. May 17, 2006 #2
    [tex] KMnO_{4} [/tex] is an oxidizing agent while [tex] KI [/tex] and [tex]KBr [/tex] are reducing agents. However, when redox reactions occur, it is the [tex] MnO_{4}^- [/tex] ion that is being reduced and the [tex] I^- [/tex] and [tex] Br^- [/tex] ions that are being oxidized. Since [tex]K^+ [/tex]is just a spectator ion, my guess is it's all right to leave it out of the half equations first. Once you've finished balancing them, you can then try to see if you can re-introduce them into the overall equation (but I don't think it's absolutely neccesary). This should make your work more manageable!
    Last edited: May 17, 2006
  4. May 18, 2006 #3
    Find a set of solubility rules should help you with the ppt part. I think MnSO4 is insoluble.
    As a rule, anything with NO3 should be soluble. Things involving Cl- should be soluble, and things with Group I metals are usually soluble.
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