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chemistry--double indicator titration

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    hello anyone know how to do the attach question and if HCL is added to a solution contain NaOH and Na2CO3. which two will react first and why. please help me .thanks!!
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    (Original post by KULER)
    hello anyone know how to do the attach question and if HCL is added to a solution contain NaOH and Na2CO3. which two will react first and why. please help me .thanks!!
    Hi
    In the first titration the following happens:
    NaOH + HCl --> NaCl + H2O
    and
    Na2CO3 + HCl --> NaHCO3 + NaCl


    In the second titration the following happens:
    NaHCO3 + HCl --> NaCl + CO2 + H2O

    So 2nd titre gives moles of NaHCO3
    Which is equal to the moles of Na2CO3

    and then the moles of NaOH = moles of HCl in first titre - moles of Na2CO3

    Then multiply by molar masses and divide by volume used and you have the answers.


    This page shows you the titration curve, which should help you understand why the reactions occur in the order they do. Phenolphthalein changes colour at high pH and methyl orange changes colour at low pH: https://docs.google.com/viewer?a=v&q...UIrHDMgHR6NKQg

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Updated: April 7, 2012
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