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Problems1 - 4 At a pH of 4.80 the concentration of lactic...

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Homework Assignment 01 Fall 2008 Acid-Base Equilibria & the Henderson-Hasselbalch Equation 1. Phosphoric acid is a polyprotic acid that can undergo three ionization reactions as illustrated below. (a) What species of phosphoric acid is dominant at pH 10 ? (b) At what pH is the [H 3 PO 4 ] equal to the [H 2 PO 4 ] ? 2. Imidazole has a pKa of 7.0, whereas the pKa for n- butyric acid is 4.82. Which of these two compounds should be used to prepare a buffer with a pH of 7.1? 3. For the amino acid glycine, pKa 1 and pKa 2 are 2.34 and 9.60, respectively. (a) Is the amino group of glycine protonated at pH 6? (b) Draw the structure of the form of glycine that predominates at pH 11.5?
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Unformatted text preview: 4. At a pH of 4.80, the concentration of lactic acid and lactate are 0.010 M and 0.087 M, respectively. What is the pKa for lactic acid? 5. The pKa for acetic acid is 4.76. What is the pH of a solution containing 0.10 M acetic acid and 0.20 M sodium acetate? 6. Calculate the concentrations of acetic acid and acetate required to prepare a 200 mM buffer solution with a pH of 5.0. The pKa for acetic acid is 4.76. 7. Benzoic acid has a pKa of 4.20. What is the ratio of benzoic acid and benzoate at a pH of 4.20? pKa 1 = 2.15 pKa 2 = 7.20 pKa 3 = 12.37...
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