pH = 11.60
[ A- ] = 0.392 M
[H+] = 10^-pH
         =
10^-11.60
          =
2.5 x 10^-12 M
[OH-] = 1.0 x 10^-14 / 2.5 x 10^-12 = 4 x 10^-3 M
A-Â Â + H2OÂ Â ---------------------> AH +
OH-
0.392Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
0Â Â Â Â Â Â Â Â Â 0
0.392-x                                   Â
x          x
x = [OH-] = 4 x 10^-3 M
Kb = x^2 / 0.392 -x
kb = (4 x 10^-3)^2 / (0.392 - 4 x 10^-3)
Kb = 4.12 x 10^-5
