Question

Cocaine is a weak base (Figure see below) with pKb = 5.59. Cocaine has local anesthetic effect (local anesthetic) but is also a narcotic.
 
a) Calculate the ratio of the concentration of cocaine and its conjugated acid in a solution which has. pH = 7.40 (that of blood) ii. pH = 1.50 (that of the stomach)
 
b) If cocaine have the best solubility in an aqueous solution with pH 7.40 or pH = 1.50. Explain your answer.