Experiment 2 · Titration Curve Simulator

Add a strong base (or acid) to a weak acid and watch the pH curve form. Find the buffering region, the half-equivalence point (where pH = pKa), and the equivalence point.

Weak-acid buffer system

Analyte (the weak acid in the flask)

Concentration C_a (mol/L)

Volume V_a (mL)

Titrant concentration C_t (mol/L) The strong reagent in the burette.

Titrant type

Strong base (NaOH) Strong acid (HCl)

Titrant added V_t

0.0 mL

Drag to dose, or animate the whole titration.

Current pH

—

Titrant added: —
pK_a (region): —
Equivalence volume V_eq: —
Half-equivalence V_eq/2: —
Buffer capacity β: —

The curve is flattest — and the buffer capacity β is largest — right at pH = pK_a (the half-equivalence point). That is the heart of the buffering region, roughly pK_a ± 1.

Teaching model: activity is treated as equal to concentration and ionic-strength effects are ignored. Each buffer is modelled with a single relevant pK_a, and the strong titrant is assumed fully dissociated. Real titration curves shift a little with ionic strength and (for polyprotic acids) show extra features.