What is the pH of 0.35M KOBr solution? For HOBr Ka=2.5×10^-9

Question

A. 8.60

B. 9.06

C. 11.07

D 11.53

E. 13.54

Answer 1

KOBr is the salt of a strong base and a weak acid so pH would be alkaline, >7.

Kb = 10-14/2.5x10-9 = 4x10-6

OBr- + H2O ==> HOBr + OH-

4x10-6 = (x)(x)/0.35

x2 = 1.4x10-6

x = [OH-] = 5.85

pH = 8.14 ANSWER A (maybe need to use the quadratic, which I'm not going to do)