𧫠Titration Calculator
Molarity, volume, and equivalence points.
How to Use This Calculator
Choose what to solve for, enter the known molarity and volumes plus the stoichiometric ratio. You also get the equivalence point pH range for your titration type.
The Formula
Unknown M = (known M x known V) / (unknown V x ratio)
At equivalence, titrant moles times the stoichiometric ratio equal analyte moles. Volumes must be in the same units; the ratio handles non-1:1 reactions like H2SO4 (2:1).
Worked Example
25 mL of 0.1 M NaOH neutralizes 20 mL HCl (1:1): M(HCl) = 0.1 x 25 / 20 = 0.125 M. Strong/strong, so equivalence at pH 7.
Choosing an Indicator
Indicators change color over a pH range, and that range must bracket the equivalence point. Phenolphthalein (colorless to pink, pH 8.2 to 10) suits weak acid/strong base titrations where equivalence is basic. Methyl orange (red to yellow, 3.1 to 4.4) suits strong acid/weak base. For strong/strong, bromothymol blue or phenolphthalein both work since the pH jump spans 4 to 10.
Primary Standards
Titrant solutions are standardized against primary standards: ultra-pure, stable compounds weighed precisely. Potassium hydrogen phthalate (KHP) is the classic standard for bases. You cannot just trust the label molarity of NaOH solution because it absorbs CO2 from air and its concentration drifts; standardize it first, then titrate your unknown.
Back Titrations
When the analyte reacts too slowly or will not dissolve, add a known excess of titrant and titrate what remains. Antacid tablets are analyzed this way: dissolve in excess HCl, then titrate the leftover acid with NaOH. The difference reveals how much acid the tablet neutralized.
Acid Rain Monitoring
Environmental labs titrate rainwater samples to track acid rain trends over decades. Automated titrators handle hundreds of samples with precision no human hand-titration can match. The data showed real improvement after clean air legislation cut sulfur emissions, a rare clear win for environmental chemistry.
Frequently Asked Questions
What is the equivalence point?
The point where moles of titrant exactly neutralize the analyte. For strong acid plus strong base it is pH 7. For weak acid plus strong base it is above 7 because the conjugate base hydrolyzes.
How do I find unknown molarity from titration?
M1V1 = M2V2 at equivalence for 1:1 stoichiometry. Multiply by the mole ratio for other ratios. Enter your known values and this calculator solves it.
What indicator should I use?
Pick one that changes near the equivalence pH: phenolphthalein (8.2-10) for weak acid/strong base, methyl orange (3.1-4.4) for strong acid/weak base, bromothymol blue (6-7.6) for strong/strong.
Why does the pH jump at equivalence?
Near equivalence, each drop of titrant swings the ratio of acid to conjugate base enormously. The logarithmic pH scale turns that into a near-vertical jump of several pH units.
What is a back titration?
When the analyte reacts slowly or is insoluble, you add excess titrant and titrate the leftover. Useful for antacids and aspirin analysis. The math is the same, applied twice.