Question

Can someone please help me explain why this is wrong?

A 0.204 M solution of a weak base has a pH of 10.29. What is the base hydrolysis constant, Kb, for the weak base? Kb = 1.8 X10-7

Answer 1

pH + pOH = 14

10.29 + pOH = 14

pOH = 3.71

[OH-] = 10^-3.71

          = 1.95 x 10^-4 M

Kb = [OH-]^2 / C - OH-

Kb = (1.95 x 10^-4)^2 / 0.204 - 1.95 x 10^-4

Kb = 3.80 x 10^-8 / 0.204

Kb = 1.87 x 10^-7

answer : 1.87 x 10^-7 (or) 1.9 x 10^-7

note : you may be wrong only at significant figures remaining is correct