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Titration lab with potassium permanganate

  1. Nov 7, 2011 #1
    1. The problem statement, all variables and given/known data
    1.The primary standard in thiss experiment is ammonium iron(II) sulphate hexahydrate, (NH4)2Fe(SO4)2*6H2O. Calculate the number of millimoles of ammonium iron(II) sulphate hexahydrate in a 1.0000g sample.

    2.Give the balanced equation for oxidation of iron(II) ion by permanganate and find how many millimoles of permanganate ion react with one millimole of ammonium iron(II) sulphate.

    3.Calculate the number of millimoles of permanganate ion that titrates 1.0000g of ammonium iron(II) sulphate.

    2. Relevant equations
    The balanced equation for 2 is MnO4^- + 8H^+ + 5Fe^2+ ---> Mn^2+ + 4H20 + 5Fe^3+

    3. The attempt at a solution
    For #1, would I just use 1.0000g x (1mol/molar mass of ammonium iron(II) sulphate hexahydrate) then change the answer into millimoles. I get 2.5501millimoles

    For #2, would I use the moles/millimoles I got for #1 and use the ratio from the equation? But where does the ratio come from if ammonium iron(II) sulphate isnt in the balanced equation?
  2. jcsd
  3. Nov 8, 2011 #2


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    Staff: Mentor

    You know how to calculate number of moles of Fe2+ per mole of Mohr's salt, but you don't know how to calculate number of moles of Mohr's salt that contain a mole of Fe2+? It is the same thing, just the ratio is reversed (which doesn't matter here, as 1/1=1).
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