# Data table 1 on your printed graph one of the two

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Chapter 13 / Exercise 1
Mathematical Practices, Mathematics for Teachers: Activities, Models, and Real-Life Examples
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Data Table 1.On your printed graph, one of the two equivalence points is usually more clearly defined than the other; the two-drop increments near the equivalence points frequently result in larger increases in pH (a steeper slope) at one equivalence point than the other. Indicate the more clearly defined equivalence point (first or second) in your data table. 2.Use your graph and data table to determine the volume of NaOH titrant used for the equivalence point you selected in Step 1. To do so, examine the data to find the largest increase in pH values during the 2-drop additions of NaOH. Find the NaOH volume just beforethis jump. Then find the NaOH volume afterthe largest pH jump. Underline both of these data pairs on the printed data table and record them in your data table. 3.Determine the volume of NaOH added at the equivalence point you selected in Step 1. To do this, add the two NaOH volumes determined in Step 2, and divide by two. For example: = 12.39 mL 4.Calculate the number of moles of NaOH used at the equivalence point you selected in Step 1. 5.Determine the number of moles of the diprotic acid, H2X. Use Equation 3 or Equation 5 to obtain the ratio of moles of H2X to moles of NaOH, depending on which equivalence point you selected in Step 1.
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Chapter 13 / Exercise 1
Mathematical Practices, Mathematics for Teachers: Activities, Models, and Real-Life Examples
Larson Expert Verified
4 6.Using the mass of diprotic acid you measured out in Step 1 of the procedure, calculate the molecular weight of the diprotic acid, in g/mol. 7.From the following list of five diprotic acids, identify your unknown diprotic acid. Diprotic Acid Formula Molecular weight Oxalic Acid H2C2O490 Malonic Acid H2C3H2O4104 Maleic Acid H2C4H2O4116 Malic Acid H2C4H4O5134 Tartaric Acid H2C4H4O6150 8.Determine the percent error for your molecular weight value in Step 6. 9.For the alternateequivalence point (the one you did not use in Step 1), use your graph and data table to determine the volume of NaOH titrant used. Examine the data to find the largest increase in pH values during the 2-drop additions of NaOH. Find the NaOH volume just before and after this jump. Underline both of these data pairs on the printed data table and record them in the Data and Calculations table. Note: Dividing or multiplying the other equivalence point volume by two may help you confirm that you have selected the correct two data pairs in this step. 10.Determine the volume of NaOH added at the alternate equivalence point, using the same method you used in Step 3. 11.On your printed graph, clearly specify the position of the equivalence point volumes you determined in Steps 3 and 10, using dotted reference lines like those in Figure 1. Specify the NaOH volume of each equivalence point on the horizontal axis of the graph. Data Table Mass of diprotic acidg Concentration of NaOHM 1. Equivalence point (indicate which one you will use in the calculations below)first equivalence point ——or second equivalence point ——2. NaOH volume added before and after the largest pH increase______ mL ______mL 3. Volume of NaOH added at the equivalence pointmL
5 4. Moles of NaOHmol 5. Moles of diprotic acid, H2Xmol 6. Molecular weight of diprotic acidg/mol
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