pOH = 14 - 9.5 = 4.5
c(OH-) = 10^-4.5
. B-+H2O = HB +OH-
平衡c(mol/L)0.3-c(OH-) c(OH-) c(OH-)
Kb = c(OH-)^2／[0.3-c(OH-)] = 3.3×10^-9
Ka = Kw／Kb = 3×10^-6