Titration Calculator

Valence represents how many H⁺ or OH⁻ ions each molecule of acid or base can donate — HCl and NaOH each have a valence of 1, but H₂SO₄ has an acid valence of 2 because it can donate two protons per molecule, and Ca(OH)₂ has a base valence of 2. Leaving valence at the default 1 for a polyprotic acid or a base like Ca(OH)₂ will make the calculator overstate the equivalence volume, since it will assume each molecule neutralizes only half of what it actually can.

The chart is built assuming a strong acid reacting with a strong base, where the only species left at equivalence are spectator ions that don't affect pH, so the curve is forced through neutral pH 7 exactly where moles of acid and moles of base added are equal. If either your acid or base is actually weak, the true equivalence point sits above or below pH 7 because the leftover conjugate acid or base reacts with water — something this simplified curve doesn't model.

Equivalence Volume is just the volume of base titrant needed to reach the equivalence point, calculated from Ma × Va × na = Mb × Vb × nb. Total Volume at Equiv. adds that base volume to the original acid volume in the flask, giving the full volume of the combined solution once neutralization is complete — useful if you need to know the final concentration of any spectator ions in solution.

The math only cares about total moles of H⁺ versus total moles of OH⁻ at equivalence, so the labels of 'acid in the flask, base in the burette' reflect the most common lab setup but the equivalence volume calculation itself is symmetric — swapping which species is the analyte and which is the titrant doesn't change the underlying mole-balance formula, only which volume you're solving for.