An ecobotanist separates the components of a tropical bark extract by chromatography. She discovers a large proportion of quinidine, a dextrorotatory isomer of quinine used for control of arrhythmic heartbeat. Quinidine has two basic nitrogens (Kb1 = 4.0 10-6 and Kb2 = 1.0 10-10). To measure the concentration, she carries out a titration. Because of the low solubility of quinidine, she first protonates both nitrogens with excess HCl and titrates the acidified solution with standardized base. A 31.35 mg sample of quinidine (M = 324.41 g/mol) is acidified with 6.55 mL of 0.150 M HCl?
a) How many mL of 0.0152 M NaOH are needed to titrate the excess HCl? ___mL
b) How many additional milliliters of titrant are needed to reach the first equivalence point of quinidine dihydrochloride? ____mL
c) What is the pH at the first equivalent point?