Titration Curve Visualizer for A-Level Chemistry

Last updated: June 2026

Use this titration curve visualizer to see how pH changes as titrant is added. It compares strong acid–strong base, weak acid–strong base and weak base–strong acid titrations.

Key takeaway: The initial solution, buffer region, half-equivalence point, equivalence point and excess-titrant region are controlled by different chemical species. The visualizer calculates each region separately.

How to use this visualizer

Choose the titration type.
Enter the analyte concentration and volume.
Enter the titrant concentration and the volume you want to inspect.
For a weak acid or weak base, enter pK_a or pK_b.
Select Visualize curve.

Table of Contents

What does a titration curve show?

A titration curve is a graph of pH against the volume of titrant added. Far from equivalence, the pH normally changes gradually. Near equivalence, a small additional volume can produce a large pH change, giving the steep section used to select an indicator.

Strong acid–strong base titration

HCl + NaOH → NaCl + H₂O

Before equivalence, excess H⁺ controls the pH. At equivalence, the pH is approximately 7.00 at 25°C. After equivalence, excess OH⁻ controls the pH.

Weak acid–strong base titration

CH₃COOH + OH⁻ → CH₃COO⁻ + H₂O

Before equivalence, the weak acid and its conjugate base form a buffer. At half-equivalence, their amounts are equal, so pH = pK_a. At equivalence, the conjugate base hydrolyses and the solution is alkaline.

Weak base–strong acid titration

NH₃ + H⁺ → NH₄⁺

Before equivalence, the weak base and its conjugate acid form a buffer. At half-equivalence, pOH = pK_b. At equivalence, the conjugate acid hydrolyses and the solution is acidic.

Equivalence and half-equivalence

c_analyteV_analyte = c_titrantV_equivalence

This visualizer assumes a 1:1 acid–base reaction. The half-equivalence point occurs at half the equivalence volume and is especially important for weak acid and weak base titrations.

Choosing an indicator

A suitable indicator changes colour within the steep pH region. Bromothymol blue is suitable for many strong acid–strong base titrations, phenolphthalein is commonly suitable for weak acid–strong base titrations, and methyl orange is commonly suitable for weak base–strong acid titrations.

Exam trap: The endpoint is the observed indicator colour change, while the equivalence point is the theoretical stoichiometric point. They should be close, but they are not the same definition.

Frequently asked questions

Why is the equivalence point not always pH 7?

A weak acid produces a basic conjugate base at equivalence, while a weak base produces an acidic conjugate acid. Only a strong acid–strong base titration is approximately neutral at equivalence at 25°C.

Why does the curve become steep near equivalence?

Very little analyte remains near equivalence. A small extra volume can therefore change the solution from analyte excess to titrant excess, causing a large pH change.

Can I use this for polyprotic acids?

No. This version assumes one acidic or basic equivalent per formula unit and a 1:1 reaction with the titrant.