The pH of a 0.10 M solution of histidine, CeH9NzO2, a weak organic base was measured at equilibrium and found to be 8.33. Calculate the hydroxide ion concentration in this solution. O a. 9.90 x 10-2M O b. 1.40 x 10-5 M O c. 2.14 x 10-6 M O d. 8.93 x 10-5M