8.5 Acid–Base Titrations

01Reading the curve

Strong acid–strong base: equivalence at pH 7, sharp jump. Weak acid–strong base: equivalence above 7, starts at higher pH, has a buffer region.

At the half-equivalence point, [HA] = [A⁻] so pH = pKa.

Choose an indicator whose pKa ≈ equivalence pH.

Worked example: Half-equivalence pH = 4.74 → Ka = 10^−4.74 = 1.8 × 10^−5 (acetic acid).

Key takeaways

Quick check

1.At half-equivalence pH = 5.0. pKa?

2.Diprotic acid titration shows how many equivalence points?

3.Best indicator for weak acid/strong base (eq. pH 8.8)?