General Chemistry • Acid Base Equilibrium
This tool handles aqueous solutions where either the anion of a weak acid (basic hydrolysis) or the cation of a weak base (acidic hydrolysis) reacts with water. It shows the hydrolysis reaction, an ICE table, and the full quadratic solution with the common \(x \approx \sqrt{K\,C_0}\) check.
Hydrolysis is the reaction of an ion with water to produce H3O+ or OH-, changing the pH of the solution. It commonly occurs for salts made from a strong acid with a weak base, or a weak acid with a strong base.
A- hydrolyzes as A- + H2O ⇌ HA + OH-. Use Kb = Kw/Ka(HA), solve Kb = x^2/(C0 - x) for x = [OH-], then compute pOH = -log10(x) and pH = 14 - pOH at 25 C.
BH+ hydrolyzes as BH+ + H2O ⇌ B + H3O+. Use Ka = Kw/Kb(B), solve Ka = x^2/(C0 - x) for x = [H3O+], then compute pH = -log10(x) and pOH = 14 - pH at 25 C.
The ICE-table substitution into K = x^2/(C0 - x) produces a quadratic in x because the ion concentration appears in both the numerator and denominator. The physically meaningful positive root gives the equilibrium [OH-] or [H3O+].
It is acceptable when x is small compared with C0 so that C0 - x ≈ C0. A common check is the 5% rule: if x ≤ 0.05 C0, the approximation is typically reasonable.