Acid-Base Titration Calculator

How this acid-base titration calculator works

This acid-base titration calculator determines the concentration of an unknown solution from its reaction with a standard solution of known concentration. The known reagent is the titrant delivered from the burette; the unknown is the analyte placed in the flask. At the endpoint, the delivered titrant volume corresponds to the amount required by the balanced reaction, allowing the analyte amount and concentration to be calculated from the recorded titration data.

The calculation is intended for common instructional and routine laboratory problems where the titrant molarity, endpoint volume, analyte aliquot volume, and titrant-to-analyte mole ratio are known. It returns analyte concentration and, when a molar mass is supplied, the mass represented by that aliquot. The curve and endpoint activity are visual aids: they connect the stoichiometric endpoint calculation with the rapid pH change expected near equivalence in the simplified model.

Acid-base titration errors often arise before any arithmetic begins: titrant and analyte may be reversed, milliliters may be used without conversion, or a non-1:1 reaction may be treated as a 1:1 neutralization. The labeled fields on this page separate those quantities and require the reaction ratio explicitly. Review the balanced equation and the burette readings before relying on the calculated concentration.

Acid-base titration inputs and what they mean

For an acid-base titration, the first field is the known titrant concentration, $C_t$, in moles per liter. The titrant volume, $V_t$, is the milliliters actually delivered to the endpoint—normally the final burette reading minus the initial reading. The analyte volume, $V_a$, is the milliliters of unknown solution initially pipetted or otherwise measured into the flask.

For this titration calculation, the stoichiometric ratio means moles of titrant per mole of analyte in the balanced reaction. A simple HCl–NaOH neutralization uses a ratio of 1. A diprotic acid neutralized by a strong base can require a ratio of 2 because each mole of acid requires two moles of hydroxide. The calculator cannot infer that ratio from chemical names, so an incorrect ratio changes the reported analyte concentration even when the measured volumes are accurate.

The optional molar-mass entry applies only after the acid-base titration calculation has found analyte moles. It converts those moles to grams for the aliquot in the flask and does not alter the calculated molarity. Leave it blank when the concentration and amount in moles are the only required results.

Acid-base titration core formula

At the acid-base titration endpoint, the reacting amounts must satisfy the balanced-reaction stoichiometry:

Formula: C_t V_t = r C_a V_a

$C_t{V}_t=r{C}_a{V}_a$

Solving the titration relationship for the unknown analyte concentration gives:

Formula: C_a = (C_t V_t) / (r V_a)

$C_a=\frac{C_t{V}_t}{r{V}_a}$

In these acid-base titration equations, $C_t$ is titrant concentration, $V_t$ is endpoint titrant volume, $V_a$ is analyte aliquot volume, $r$ is the titrant-to-analyte mole ratio, and $C_a$ is the unknown analyte concentration. Although burette and pipette volumes are entered in milliliters, the script converts each volume to liters before calculating moles from molarity.

The titrant moles are first obtained from $n_t=C_t{V}_t$. Dividing by the reaction ratio gives analyte moles, and dividing those moles by the analyte volume gives analyte concentration. When molar mass is entered, the calculator multiplies analyte moles by grams per mole to report the mass in that specific titrated aliquot.

Worked example: monoprotic acid titrated with sodium hydroxide

In this acid-base titration example, 25.0 mL of an unknown monoprotic acid is titrated with 0.100 M sodium hydroxide, reaching the endpoint after 30.0 mL of base is delivered. One mole of NaOH reacts with one mole of the acid, so the stoichiometric ratio is 1. Enter 0.100 for titrant concentration, 30.0 for titrant volume, 25.0 for analyte volume, and 1 for the ratio.

The calculated acid concentration is:

Formula: C_a = (0.1 × 30) / (1 × 25) = 0.12 M

$C_a=\frac{0.1\times 30}{1\times 25}=0.12M$

The unknown acid is therefore 0.12 M. Its amount in the 25.0 mL aliquot is 0.12 × 0.025 = 0.003 mol. With an analyte molar mass of 98.08 g/mol, that aliquot would contain about 0.294 g. The endpoint volume and the 1:1 reaction relationship together reveal the amount of acid in the measured sample.

How to interpret the acid-base titration result

The acid-base titration result box reports the concentration of the analyte in the flask, not the known titrant concentration in the burette. Its mole value is limited to the analyte aliquot volume entered in the form, and an optional mass value also refers to that same aliquot. If the aliquot was diluted from a stock solution or represents only part of a larger sample, perform the appropriate dilution or sample-preparation calculation separately.

The acid-base titration calculation assumes that the entered endpoint volume is the delivered volume to use for the analysis. In a laboratory run, an indicator endpoint can differ slightly from the true equivalence point, and overshooting or uncertain meniscus readings affect the input volume. The stoichiometric result is still the correct calculation based on the entered data, but the precision of a reported experimental result should reflect measurement quality and the suitability of the indicator.

Acid-base titration curve and model assumptions

The acid-base titration curve below the form is a simplified strong-acid/strong-base educational model based on the entered quantities. It depicts pH changing gradually away from equivalence and sharply near it, illustrating why additions should be made dropwise as the endpoint approaches. It is not an equilibrium calculation for weak acids, weak bases, buffers, or polyprotic systems.

The concentration calculation itself remains applicable when the balanced reaction and entered mole ratio are correct. Experimental problems such as burette-reading errors, air bubbles, contaminated glassware, missed dilution factors, or an incorrectly balanced equation cannot be corrected by the calculator. Use the result as a stoichiometric check alongside careful titration technique and documented laboratory observations.

Acid-base titration reference formulas and relationships

These acid-base titration relationships state the concentration, mole, mass, volume-conversion, and simplified pH expressions used to explain the calculator and its curve model.

Formula: C_t = n_t / V_t

$C_t=\frac{n_t}{V_t}$

Formula: C_a = n_a / V_a

$C_a=\frac{n_a}{V_a}$

Formula: n_t = C_t V_t

$n_t=C_t{V}_t$

Formula: n_a = n_t / r

$n_a=\frac{n_t}{r}$

Formula: n_a = C_a V_a

$n_a=C_a{V}_a$

Formula: m = n_a M

$m=n_{a}M$

Formula: V_t(L) = V_t(mL) / 1000

$V_t\left(L\right)=\frac{V_t\left(\mathrm{mL}\right)}{1000}$

Formula: V_a(L) = V_a(mL) / 1000

$V_a\left(L\right)=\frac{V_a\left(\mathrm{mL}\right)}{1000}$

Formula: C_t V_t = r C_a V_a

$C_t{V}_t=r{C}_a{V}_a$

Formula: C_a = (C_t V_t) / (r V_a)

$C_a=\frac{C_t{V}_t}{r{V}_a}$

Formula: r = n_t / n_a

$r=\frac{n_t}{n_a}$

Formula: n_t = r n_a

$n_t=r{n}_a$

Formula: n_a = (C_t V_t) / r

$n_a=\frac{C_t{V}_t}{r}$

Formula: C_a V_a = (C_t V_t) / r

$C_a{V}_a=\frac{C_t{V}_t}{r}$

Formula: m = (C_t V_t M) / r

$m=\frac{C_t{V}_{t}M}{r}$

Formula: pH = - log_10([H^+])

$\mathrm{pH}=-{\log }_{10}\left(\right[H^{+}\left]\right)$

Formula: pOH = - log_10([OH^-])

$\mathrm{pOH}=-{\log }_{10}\left(\right[{\mathrm{OH}}^{-}\left]\right)$

Formula: pH + pOH = 14

$\mathrm{pH}+\mathrm{pOH}=14$