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Weak Acid Titration

  • Page ID
    282816
  • Titration of Weak Acid with Strong Base

    Consider the titration of 50.00 mL of 0.02000 M MES with 0.1000 M NaOH. MES is an abbreviation for 2-(N-morpholino)ethanesulfonic acid, which is a weak acid with pKa = 6.27.

    1. What is the molecular structure of MES?




     

    1. What is the chemical reaction between MES and NaOH? What is the net ionic equation for this reaction?




     

    1. Before adding NaOH,
      1. What species are present in the solution?

         

      2. What are the resources for those species?

         

      3. What type of the solution is this solution?

         

      4. What is the pH of this solution?





     

    1. 3.00 mL of NaOH have now been added to the MES solution.
      1. Which one is the limiting reagent for the reaction, MES or NaOH?

         

      2. What species are present in the solution?

         

      3. What are the resources for those species?

         

      4. What type of the solution is this solution?

         

      5. What is the pH of this solution?





     

    1. 10.00 mL of NaOH have now been added to the MES solution.
      1. Which one is the limiting reagent for the reaction, MES or NaOH?

         

      2. What species are present in the solution?

         

      3. What are the resources for those species?

         

      4. What type of the solution is this solution?

         

      5. What is the pH of this solution?

     

     

     

     

     

     

     

    1. 10.10 mL of NaOH have now been added to the MES solution.
      1. Which one is the limiting reagent for the reaction, MES or NaOH?

         

      2. What species are present in the solution?

         

      3. What are the resources for those species?

         

      4. What type of the solution is this solution?

         

      5. What is the pH of this solution?

     

     

     

     

     

     

     

     

     

    1. Now more calculations on the pH of this titration have been calculated as below.
      1. Sketch a graph showing the pH of the system vs. the volume of NaOH added (all values are adopted from Daniel Harris Quantitative Chemical Analysis, 8th ed).

        mL base added

        pH

        mL base added

        pH

        0.00

        3.99

        10.00

        9.25

        0.50

        4.99

        10.10

        10.22

        1.00

        5.32

        10.50

        10.91

        2.00

        5.67

        11.00

        11.21

        3.00

        5.90

        12.00

        11.50

        4.00

        6.09

        13.00

        11.67

        5.00

        6.27

        14.00

        11.79

        6.00

        6.45

        15.00

        11.88

        7.00

        6.64

        16.00

        11.95

        8.00

        6.87

         

         

        9.00

        7.22

         

         

        9.50

        7.55

         

         

        9.90

        8.27

         

         

         

         

         

         

         

         

         

         

         

         

         

         

         

         

         

         

         

      2. Do you see different regions of this curve?

         

         

         

         

      3. Where is the equivalence point? What is the volume of NaOH at the equivalence point?

         

         

         

         

         

         

      4. Can you find out the pKa point for MES? What is the volume of NaOH at the equivalence point?

         

         

         

         

         

         

         

      5. What is the relationship between the volume of NaOH at the equivalence point and the volume of NaOH at the MES pKa point?

     

     

     

     

     

     

     

     

     

    Summary of Titration of Weak Acid with Strong Base

    Regions

    System

    pH Determination

     

     

     

     

     

     

     

     

     

     

     

     

    Contributors and Attributions

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