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Homework Help: Very confused in chemistry?

  1. Mar 26, 2010 #1
    1. The problem statement, all variables and given/known data

    Calculation of the number of moles of IO3- used in the titration(i.e. in the Erlenmeyer flask):
    KIO3(s) → K+(aq) + IO3-(aq): balanced eqn of dissolving KIO3 in water

    1. Calculate the moles of KIO3 used: Molecular weight of KIO3 = 214.0011 g/mol
    Amount of KIO3 used in grams = 0.0356g
    # of moles = 0.0356g/(214.0011g/mol) (grams cancels out) = 1.6635 × 10^-5 moles
    The mole ratio is 1:1:1. So # of moles of KIO3 will be equal to # of moles of IO3-

    2. Calculate the Molarity
    Amount of dH2O used for dissolving = 100mL = 0.1L
    Molarity = (moles of solute) / (volume of solution in Liters) = 1.6635 × 10^-5 moles/0.1L
    = 1.6635 × 10^-4 moles/L
    I did untill this. But in the question, it says that <Calculate the # of moles of IO3- in the Erlenmeyer flask> And in the Erlenmeyer flask, there was 10mL of KIO3 solution, and other solution of 54ml.

    And my question is, do I have to multiply the molarity I gained by calculation by 0.064mL (because (10ml+54ml)/1000 = 0.064L=amount in Erlenmeyer flask) to gain the # of moles of IO3- in the Erlenmeyer flask, Or can I just multiply the molarity by 10mL Or am I doing wrong??
    Please help!!!
  2. jcsd
  3. Mar 28, 2010 #2


    User Avatar

    Staff: Mentor

    10 mL - that was the amount of solution of iodate transferred, right? You have not transferred 64 mL, or any other volume.

  4. Mar 28, 2010 #3
    I get it. I was confused when my lab TA emphasized "in the Erlenmeyer flask", so i thought she might mean something else. :)
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