Titration Curve Calculator
pH at any point, including the equivalence point that is not 7.
Work out Titration Curve. pH at any point, including the equivalence point that is not 7. Written for the bench, not the exam hall.
Acetic 1.8e-5, formic 1.8e-4, benzoic 6.3e-5.
pH at this point
4.74
Half-equivalence — pH equals pKa exactly · equivalence at 25 mL
A weak acid titration has four distinct regions and each needs different chemistry: the weak acid alone at the start, the buffer region where Henderson-Hasselbalch applies, the equivalence point where only the conjugate base remains, and excess strong base after it. Two points are worth memorising. At half-equivalence the pH equals the pKa exactly, which is how pKa values are measured. And the equivalence point of a weak acid is BASIC, not pH 7 — what is left in the flask is the conjugate base, which hydrolyses water. Expecting 7 there is the commonest misconception about titration curves. That is also why indicator choice matters: phenolphthalein changes around pH 8.3 and suits a weak acid against strong base, while methyl orange at 3.7 would signal the end point far too early.
How the Titration Curve Calculator works
Enter the acid, the base and how much has been added, and this returns the pH along with which region of the curve you are in. A weak acid's equivalence point is basic rather than neutral, and the page is explicit about why.
Also known as: weak acid strong base titration calculator · ph during titration calculator · equivalence point ph calculator · half equivalence point calculator
Frequently asked questions
What is the pH at the equivalence point of a weak acid?
Above 7, not equal to it. All the acid has been converted to its conjugate base, which hydrolyses water and generates hydroxide. Acetic acid against sodium hydroxide equilibrates around pH 8.7.
What happens at the half-equivalence point?
The acid and its conjugate base are present in equal amounts, so the Henderson-Hasselbalch log term vanishes and pH equals pKa exactly. That is the standard way pKa values are measured.
Which indicator should I use?
One that changes colour near the equivalence pH. Phenolphthalein at 8.3 suits a weak acid against a strong base; methyl orange at 3.7 would signal the end point far too early and give a low titre.
Why does the pH jump so sharply near equivalence?
Because the buffer runs out. Right up to equivalence the mixture resists change, and once the last of the acid is consumed each additional drop of base has nothing left to neutralise it.
Put this calculator on your own site
Free to use, on any site, commercial or not. Paste this where you want it to appear. It is a plain iframe, so it works in WordPress, Squarespace, Wix, Webflow, Ghost and anything else that accepts HTML.
<iframe src="https://www.thecalclibrary.com/embed/titration-curve-calculator" width="100%" height="640" style="border:1px solid #e2e8f0;border-radius:12px" loading="lazy" title="Titration Curve Calculator"></iframe>
<p style="font:13px/1.5 system-ui,sans-serif;margin:6px 0 0;color:#64748b">Powered by <a href="https://www.thecalclibrary.com/titration-curve-calculator" style="color:#64748b">Titration Curve Calculator</a> from The Calc Library</p>The only condition is that the credit line below the frame stays in place. That one line is what pays for the tool being free — it is how anyone else finds it.