Titration Calculator
Titration is a quantitative analytical technique in which a solution of known concentration (the titrant) is used to determine the unknown concentration of another substance (the analyte). This calculator finds both the moles of base used and the molar concentration of the acid sample, assuming a 1:1 stoichiometric ratio.
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Formula
M_acid = M_base × V_base / V_acid
At the equivalence point of a 1:1 neutralization, moles of base equal moles of acid: M_base × V_base = M_acid × V_acid. Rearranging gives M_acid = M_base × V_base / V_acid. Both volumes must be in the same units — this calculator accepts mL and converts to liters internally. For reactions with stoichiometric ratios other than 1:1, multiply M_acid by the mole ratio (e.g., H₂SO₄ + 2 NaOH would give M_H₂SO₄ = M_base × V_base / (2 × V_acid)).
How to use the Titration Calculator
- 1
Enter your concentration of base (titrant)
Value should be in M.
- 2
Enter your volume of base used
Value should be in mL.
- 3
Enter your volume of acid sample
Value should be in mL.
- 4
Read your results instantly
Results update in real time as you type.
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How titration works
In a typical acid-base titration, you place a precisely measured volume of acid (the analyte) in an Erlenmeyer flask and add a few drops of indicator such as phenolphthalein. You then slowly add the base (the titrant) from a burette, swirling the flask continuously. Initially the base is neutralized as fast as you add it. Near the equivalence point — where moles of base exactly equal moles of acid — the pH changes very rapidly with each drop added. The indicator changes color at the endpoint, which is as close to the equivalence point as you can detect visually. The volume of base delivered from the burette at the endpoint is the volume you record and use in the calculation.
Sources of error and how to minimize them
Titration accuracy depends on several factors. Indicator choice matters: phenolphthalein changes at pH 8.2–10, which is suitable for strong acid-strong base titrations but may introduce a systematic error for weak acid-strong base or weak acid-weak base systems. The endpoint should be identified as the first permanent color change, not a deep permanent color — overshooting adds excess base. Parallax error when reading the burette meniscus is reduced by reading at eye level and using the bottom of the meniscus for clear solutions. Rinsing the burette with the titrant solution before filling it prevents dilution errors. Performing three concordant titrations (agreeing within ±0.10 mL) and averaging the volumes is standard practice for reliable results.
Tips & Insights
Run a rough titration first
Perform a quick 'scout' titration to find the approximate endpoint, then do two or three careful titrations adding base dropwise near the endpoint. This saves reagent and improves precision.
Rinse your burette with titrant before filling
Any water remaining in the burette dilutes the titrant and lowers the effective concentration, introducing a systematic error. Rinse twice with small volumes of the titrant solution before filling to the zero mark.
Adjust for non-1:1 stoichiometry
This calculator assumes one mole of base reacts with one mole of acid. For diprotic acids like H₂SO₄ or H₂CO₃, divide the calculated acid molarity by the number of acidic protons per molecule.
Worked Examples
Standard NaOH titration of HCl
Moles of base = 0.0025 mol; Acid concentration = 0.125 M HCl — consistent with a common introductory lab result.
Back-titration of weak acid
Moles of base = 0.000925 mol; Acid concentration = 0.0925 M — a typical dilute acid concentration in a research sample.
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Frequently Asked Questions
What is the equivalence point?
The equivalence point is when exactly enough titrant has been added to completely react with all of the analyte. For a 1:1 acid-base reaction, moles of acid equal moles of base at the equivalence point.
What is the difference between endpoint and equivalence point?
The equivalence point is the theoretical stoichiometric completion. The endpoint is the experimentally observed color change of the indicator. A well-chosen indicator makes these nearly identical, but they are not the same.
How do I choose the right indicator?
Choose an indicator whose pKa is close to the equivalence point pH. For strong acid-strong base titrations, almost any indicator works. For weak acid-strong base, use phenolphthalein. For strong acid-weak base, use methyl orange.
Can this formula be used for oxidation-reduction titrations?
No. Redox titrations use equivalents rather than moles and require knowledge of the number of electrons transferred. This calculator is specific to acid-base neutralization reactions.
Why do I need three concordant titrations?
Repeating titrations and averaging reduces random error. Results that agree within 0.10 mL of each other are considered concordant. Outlier readings (caused by overshooting the endpoint) should be discarded.
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