Weak Base pH Calculator
Calculate the pH of a weak base solution from Kb and initial concentration
B + H2O = BH+ + OH-
Common Weak Bases:
pH
11.1276
pOH
2.8724
[OH-]
1.3416e-3 M
pKb
4.7447
% Ionization
1.3416%
Equilibrium Concentrations:
[B] = 9.8658e-2 M
[BH+] = 1.3416e-3 M
[OH-] = 1.3416e-3 M
[H+] = 7.4536e-12 M
Conjugate Acid:
pKa (conjugate) = 9.2553
pKa + pKb = 14
Calculating Weak Base pH
For a weak base B with initial concentration C and dissociation constant Kb, the pH is calculated by first finding pOH from the equilibrium expression Kb = [BH+][OH-]/[B], then using pH = 14 - pOH.
Approximation Method
[OH-] = sqrt(Kb x C)
Valid when % ionization < 5%
Exact (Quadratic) Method
[OH-] = (-Kb + sqrt(Kb^2 + 4KbC)) / 2
Always accurate
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Editorial Note
MyCalcBuddy Editorial Team
This page is maintained as an educational calculator reference.
Formula Source: Chemistry: The Central Science
by Brown, LeMay, Bursten