11-21. The baseNa+A-, whose anion is dibasic, was titrated withHCI to give curveb in Figures 11-4. Is the first equivalence point Hthe isoelectric point or the isoionic point?

Short Answer

Expert verified

The first equivalence point is the isoionic point.

Step by step solution

01

The Isoinic point:

The number where a zwitterion molecule seems to have an identical number of positive and negative charges and also no adherent ionic species is found as the isoionic point.

02

The Isoelectric point:

The isoelectric point (IEP) is the pH value at which the zeta potential is zero. The may be calculated using the Nicomp Z3000 system by titrating the sample and monitoring the zeta potential as a function of pH. Coffee-mate creamer was made by combining 0.1 g with 200 mL of DI water.

The pH number at where the zeta potential is 0 is termed as the isoelectric point (IEP) . Using the Nicomp Z3000 system, the can be estimated by titrating the sample and checking the zeta potential as a function of pH. Coffee-mate creamer was made by combining 0.1 g with 200mL of DI water.

03

the first equivalence point  the isoelectric point or the isoionic point:

The pH at the first equivalence point can be calculated by calculating the molarity of the pure HCI The average charge is then positive and we can conclude that the first equivalence point is the isoionic point.

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Most popular questions from this chapter

The balance says that you have weighed out 1.023 g of tris tostandardize a solution of HCl. Use the buoyancy correction in Section 2-3 and the density in Table 11-4 to determine how many grams you have really weighed out. The volume of HCl required to react with the tris was 28.37 mL. Does the buoyancy correction introduce a random or a systematic error into the calculated molarity of HCl? What is the magnitude of the error expressed as a percentage? Is the calculated molarity of HCl higher or lower than the true molarity?

11-20. The graph shows the titration curve for a protein containingamino acids with 16 basic and acidic substituents. The curve is smooth without clear breaks because 29 groups are titrated in thepH interval shown. The 29 endpoints are so close together that a nearly uniform rise results. The isoionic point is thepHof the pure protein with no ions present exceptH+ and OH-. The isoelectric point is the pHat which the average charge on the protein is zero. Is the average charge of the protein-positive, negative, or neutral at its isoionic point? How do you know?

Acid-base titration of the protein ribonuclease. [Data from C. T. Tanford and J. D. Hauenstein, "Hydrogen Ion Equilibria of Ribonuclease," J. Am. Chem. Soc. 1956, 78, 5287.]

Question:Effect of concentration in the titration of weak acid with strong base.Use your spreadsheet from Problem 11-66 to prepare a family of titration curves for pKa = 6, with the following combinations of concentrations: (a) Ca = 20 mM, Cb = 100 mM; (b) Ca = 2 mM, Cb = 10 mM; (c) Ca = 0.2 mM, Cb = 1 mM.

Calculate the pH at 10.0-mL intervals (from 0 to 100 mL) in the titration of 40.0 mL of 0.100 M piperazine with 0.100 M HCl. Make a graph of pH versus Va.

Effect of concentration in the titration of weak acid with strong base.Use your spreadsheet from Problem 11-66 to prepare a family of titration curves for pKa = 6, with the following combinations of concentrations: (a) Ca = 20 mM, Cb = 100 mM; (b) Ca = 2 mM, Cb = 10 mM; (c) Ca = 0.2 mM, Cb = 1 mM.

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