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Calculate the concentration of hydrogen peroxide

  1. Aug 3, 2004 #1
    can anone help me with these questions?

    a) How many moles of hydrogen peroxide react with each mole of permanganate in the titrationmoles of MnO4- per mole of H2O2

    b) Calculate the concentration of hydrogen peroxide in the 10 mL aliquot, taken from the reaction if the titration with 0.0176 M permanganate solution requires 32.8 mL to reach the end-point

    c) If the concentration of hydrogen peroxide in the 10 mL aliquot is 0.0568, calculate ln([H2O2])

    your help will be greatly appreciated!
     
  2. jcsd
  3. Aug 19, 2004 #2

    chem_tr

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    Science Advisor
    Gold Member

    Hello,

    I will try to solve the problems.

    a) How many moles of hydrogen peroxide react with each mole of permanganate in the titrationmoles of MnO4- per mole of H2O2

    My answer: As you know, peroxide reacts with permanganate to yield elemental oxygene and manganese(IV) oxide:

    2Mn(7+) + 6e(-) --> 2Mn(4+)
    3O2(2-) --> 3O2 + 6e(-)

    2KMnO4 + 3H2O2 --> 2MnO2 + 3O2 + 2KOH + 2H2O

    Thus, 2 moles of permanganate is required to oxidize 3 moles of peroxide.

    b) Calculate the concentration of hydrogen peroxide in the 10 mL aliquot, taken from the reaction if the titration with 0.0176 M permanganate solution requires 32.8 mL to reach the end-point

    My answer: I like to express the milimoles by directly multiplying the molarity and titer; so we obtain 0.0176*32.8=0,57728 milimoles of permanganate. We will multiply this value with 1.5 (as seen from the mole ratio between permanganate and peroxide in the reaction above) to learn the amount of reacted peroxide: 0.86592 milimoles of peroxide in 10 mL solution. This gives a 0,086592 M solution.

    c) If the concentration of hydrogen peroxide in the 10 mL aliquot is 0.0568, calculate ln([H2O2])

    My answer: I assume that [H2O2] is expressed as molar concentration, so we may directly calculate the ln value from this: in this way, we obtain approximately -2.868.

    I may be wrong, but I have not found any errors.

    Regards
    chem_tr
     
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