Titration Calculator
The whole run on one card: the equivalence volume from plain stoichiometry, the half-way pH that prints the pKa for free, and the pH waiting at the top.
Titration Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Monoprotic acid, monobasic base — one jump per run
- Weak-equivalence pH idealised at 25 °C, dilute
In short: 25 mL of 0.100000 mol/L acetic acid against 0.100000 mol/L NaOH: the equivalence lands at 25.000000 mL by pure mole counting. Half-way — 12.500000 mL — the flask is an equal pair and pH reads the pKa directly: 4.756000. At the equivalence the flask is 0.050000 mol/L acetate and climbs to pH 8.727485 — basic, because the conjugate base hydrolyses. A strong-acid run with no pKa ends flat: pH 7.000000 exactly.
Formula
V(eq) = C1·Va/C2 · half-way: pH = pKa · weak equivalence: pH = 7 + (pKa + log C)/2
The equivalence is stoichiometry, not equilibrium: moles of base added equal moles of acid started. The half-way point is the gift — half the acid has become its conjugate base, the pair is even, and the pH reads the pKa with no table needed. The weak-acid equivalence sits above 7 because the flask then holds only conjugate base, which quietly makes OH⁻ from water.
Worked Example
- Enter the acid’s concentration and volume.
- Enter the base concentration in the burette.
- Enter pKa for a weak acid — or leave blank for strong.
- Read the equivalence, the half-way pH, and the top.
Defaults: 0.1 mol/L, 25 mL vs 0.1 mol/L, pKa 4.756 → V(eq) 25.000000 mL, half-way pH 4.756000, top pH 8.727485. Strong-acid run: top pH 7.000000 exactly.
Strengths & Limits Of This Model
Where this engine is strong
- Half-way pKa read made explicit
- Strong/weak branches priced honestly
Where it stops
- No full curve rendering
- No activity or jump-width modelling
Practical Use Cases
Standardizing titrants
where the jump will land
pKa by burette
the half-way reading is the table
Prep planning
indicator choice near the jump
Methodology & Editorial Standards
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Titration Calculator — 8 Expert FAQs
8 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
Why is the equivalence volume plain stoichiometry?
Because neutralization is a mole-for-mole transfer: the burette catches up when the moles it delivered equal the moles in the flask — C1·Va = C2·V(eq). No equilibria, no pKa, just bookkeeping. That is why the hero card is the same arithmetic for acetic and hydrochloric: the COUNT is identical, the pH story on top of it is not.
Why does the half-way point print the pKa for free?
At half-neutralization, half the acid has become its conjugate base — the flask holds an equal pair, and the Henderson–Hasselbalch equation with a 1:1 ratio reduces to pH = pKa. It is the cheapest pKa measurement in chemistry: read the burette at half the jump, read the pH, file the table entry.
Why is the weak-acid equivalence above 7 while the strong one sits at 7?
At the equivalence the strong run holds salt water — neither Na⁺ nor Cl⁻ touches water’s own balance — so it reads neutral at 25 °C. The weak run holds pure conjugate base, which pulls a proton from water and leaves OH⁻ behind: the flask is genuinely basic. The card prices that hydrolysis with the 7 + (pKa + log C)/2 form.
Does the base concentration change the equivalence volume?
Yes — inversely. Double the burette strength and the jump arrives at half the volume. That is why standardizing the titrant (finding its true C2) is the first lab of every analytical course: the whole scale hangs on that one number.
What happens past the equivalence?
The flask contains the excess base you keep adding, and the pH climbs toward the titrant’s own strength. This page prices up to the equivalence and its top; the over-shoot region is excess-reagent arithmetic the pH page handles directly — leftover moles over total volume, logged.
Can I titrate a base with an acid instead?
The run mirrors: the equivalence volume arithmetic is identical (swap the roles), the strong pair still ends at 7, and the weak-base equivalence sits BELOW 7 by the mirror-symmetric formula. The cards here narrate acid-in-flask; the mole counting never cares which hand holds the burette.
Where do indicators fit?
An indicator is just a weak pair whose color flips near its own pKa — pick one whose flip window overlaps the jump: phenolphthalein’s window sits conveniently across the weak-acid equivalence near 8.7. The half-way card’s pKa reading, by contrast, needs a meter, not a color flip.
How does this chain to the other pages?
The equivalence volume is the dilution page’s stoichiometry wearing a burette; the half-way card IS the Henderson–Hasselbalch page with a 1:1 ratio; the equivalence pH is the hydrolysis the pH page’s weak-acid FAQ warned about. One run, three pages of doctrine.