01Partial ionization
Weak acids ionize only slightly: HA ⇌ H⁺ + A⁻, Ka = [H⁺][A⁻]/[HA]. Use an ICE table with the small-x approximation.
For weak bases: B + H₂O ⇌ BH⁺ + OH⁻, Kb. For conjugates, Ka × Kb = Kw.
02Notebook box
[H⁺] ≈ √(Ka·C).
Worked example: 0.10 M HA, Ka = 1 × 10^−5 → [H⁺] = √(10^−6) = 10^−3 → pH 3.