The structure of aspartic acid is HO2CCH2CHNH2CO2H; pKa1 = 3.86 and pKa2 = 9.82 for aspartic acid. Consider an aqueous solution prepared by dissolving 0.0400 g of aspartic acid in enough water to give 50.0 mL of solution.
(a)i. What volume of 0.0500 M NaOH must be added to remove the first acidic hydrogen from each aspartic acid molecule (i.e., to reach the first equivalence point)?
ii. What is the pH of the resultant solution at the first equivalence point? iii. The indicator phenolphthalien is colorless when added to a pH = 8 solution and red in a pH = 9.5 solution. Would phenolphthalien be a good indicator to signal that the first equivalence point had been reached and addition of titrant should stop? Justify your
choice.
(b)i. What volume of 0.0500 M NaOH must be added to remove both acidic hydrogens from each aspartic acid molecule (i.e., to reach the second equivalence point)?
ii. What is the pH of the resultant solution at the second equivalence point? iii. Would phenolphthalien be a good indicator to signal the second equivalence point?