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Homework Help: Redox Titrations Bleach! help

  1. Jan 17, 2012 #1
    Redox Titrations Bleach! help!!

    1. The problem statement, all variables and given/known data
    An unknown metal hypochlorite salt, M(ClO)2, is subjected to analysis by iodometric titration: the salt is dissolved in dilute sulfuric acid, treated with excess aqueous KI, and then titrated with Na2S2O3 in the same manner as your experiment. The unknown metal ion (M2+) is completely unreactive in the titration. However, all of hypochlorite ion bondd to the metal reacts completely with Na2S2O3. Iodemetric titration of an acidified 0.0499 g sample of M(ClO)2 required 28.42 ml of 0.05521 mol/L Na2S2O3 to reach the equivalence point. What is the identity of metal M?


    2. Relevant equations
    IO3^- + 5I^- + 6H^+ → 3I2 + 3H20
    I2 + 2S2O3^2- → 2I^- + S4O6^2-
    ClO^- + 2I^- + 2H^+ → I2 + Cl^- + H20


    3. The attempt at a solution
    So far all I have is the number of moles for Na2S2O3 = 0.001569 mol
    I have no idea where to go from there! please help

    ALSO one more question


    1. The problem statement, all variables and given/known data
    A sample of Au(ClO)3 is contaminated with LiClO. An acidified 0.2000 g sample of this mixture is treated with excess sodium iodide and subjected to iodometric titration. The sample requires 48.24 mL of 0.08893 mol/L Na2S2O3 to reach the equivalence point. Assuming that the Au^3+ and Li^+ ions are unreactive during the titration, determine the mass percent of LiClO in the sample.


    2. Relevant equations

    All the equations used in the first question!

    3. The attempt at a solution
    Only moles so far. =0.004289 mol


    Pleae help. Thanks!
     
  2. jcsd
  3. Jan 18, 2012 #2

    Borek

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    Staff: Mentor

    Re: Redox Titrations Bleach! help!!

    User stoichiometry to find out how many moles of ClO- were present in the sample of the given mass, then use this information to find out molar mass of the metal.
     
  4. Jan 18, 2012 #3
    Re: Redox Titrations Bleach! help!!

    okay that sounds easy enough, I think the main problem I have is not knowing what equation to use. Or do I set up my own stoichiometric equation adding M(ClO)2. and if I do, how do I go about doing that? Thanks!
     
  5. Jan 18, 2012 #4

    Borek

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    Staff: Mentor

    Re: Redox Titrations Bleach! help!!

    Forget about using "equations", think about it as just another stoichiometry problem.

    All titrations are nothing more but a simple stoichiometry. You know moles of this, you have to calculate corresponding moles of the other.
     
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