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Titration concentration calculation problem, NaOH and HCl/HOAc mixture, help please

  1. Oct 8, 2011 #1
    Hi, I'm in lab in which we have to titrate 0.09M NaOH into 25mL of 0.1M HCl/HOAc mixture.

    1. The problem statement, all variables and given/known data
    I need help on how to calculate the concentration of HCl and HOAc in the mixture.

    0.09M NaOH
    1st equivalence point = 14.3mL
    2nd equivalence point = 26.9mL

    Difference of two equivalence points, 14.3-26.9= 12.6mL


    2. Relevant equations
    I'm thinking to solve this problem I would have to use the dilution formula, M1V1=M2V2


    3. The attempt at a solution

    M (0.025L) = (0.09M)(0.0143L)
    M = 0.05148M HCl

    M (0.025L) = (0.09M)(0.0126L)
    M = 0.04536M HOAc

    Is this correct or am I completely off?

    Any help would be appreciated.

    Thanks
     
  2. jcsd
  3. Oct 9, 2011 #2

    symbolipoint

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    Gold Member

    Re: Titration concentration calculation problem, NaOH and HCl/HOAc mixture, help plea

    To give a simplified explanation:
    The weak acid will be picked at titrant addition to about pH of 4 to 4.5, and both the weak and strong acid will be neutralized at about pH 8 to 9. Your first equivalence point will give you moles of HOAc; your second equivalence point will give you moles of both HOAc and HCl combined. The difference will be for the moles of HCl alone.
     
  4. Oct 9, 2011 #3

    Borek

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    Staff: Mentor

    Re: Titration concentration calculation problem, NaOH and HCl/HOAc mixture, help plea

    Since when titration is identical to dilution?

    http://www.titrations.info/titration-calculation

    Formula you listed happens to be identical to the one needed in SOME cases. The longer you will believe it works always, the worse for you.
     
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