BYTETOOLS

Titration Calculator

Find an unknown acid or base concentration, or the titrant volume needed, using equivalents so polyprotic acids and dibasic bases are handled correctly.

Acid

Base (titrant)

0.0643 mol/L
Acid concentration
0.001608 mol
Moles of acid
0.003215 mol
Moles of base

Mₐ = (M_b · V_b · n_b) ÷ (Vₐ · nₐ)

  • Equivalents balance at the equivalence point: Mₐ·Vₐ·nₐ = M_b·V_b·n_b, with nₐ = 2 H⁺ per acid and n_b = 1 OH⁻ per base.
  • H⁺ available: 0.003215 mol · OH⁻ available: 0.003215 mol
  • Balanced mole ratio: 1 mol acid : 2 mol base — so 1 mole of acid react with 2 moles of base.
  • Base needed to neutralise the acid: 32.15 mL
  • Salt formed: sodium sulfate, plus water.

At the volumes entered

Exactly at the equivalence point — every H⁺ has been matched by an OH⁻. The solution now contains only sodium sulfate in 57.15 mL.

The equivalence point is where the moles of H⁺ and OH⁻ are equal; the endpoint is where your indicator changes colour, and the two only coincide if the indicator is chosen well. A strong acid with a strong base reaches equivalence at pH 7, but a weak acid titrated with a strong base lands above 7 because the salt hydrolyses — so phenolphthalein suits that case and methyl orange does not. Polyprotic acids have one equivalence point per proton; this page uses the final, complete-neutralisation point.

What is the Titration Calculator?

At the equivalence point the moles of transferable H+ equal the moles of OH-, so Ma x Va x na = Mb x Vb x nb. For sulfuric acid na is 2, so 25.00 mL of it neutralised by 32.15 mL of 0.1000 M NaOH is 0.0643 M.

  • Solves for acid or base concentration, or for either volume
  • Proton counts built in for HCl, sulfuric, oxalic, phosphoric, NaOH, Ca(OH)2 and more
  • Correct handling of polyprotic acids and dibasic bases through equivalents
  • Reports moles, equivalents, mole ratio and the salt produced
  • Excess reagent and its concentration in the combined volume
  • Everything computed locally in the browser

How to use the Titration Calculator

  1. 1

    Choose what you want to solve for: an unknown concentration, or a volume needed.

  2. 2

    Pick the acid and base from the dropdowns, or select Custom and set the proton counts yourself.

  3. 3

    Enter the concentrations and volumes you do know, in mol/L and millilitres.

  4. 4

    Read the answer, the moles on each side and the equivalence volume.

  5. 5

    Check the excess panel to see which reagent is left over at the volumes you entered.

About the Titration Calculator

The ByteTools Titration Calculator solves acid-base titrations using the equivalents relation Ma x Va x na = Mb x Vb x nb, where n is the number of protons each formula unit can donate or accept. That extra factor is what makes polyprotic acids work: sulfuric acid contributes two protons per molecule, phosphoric acid three, and the arithmetic accounts for it rather than assuming a one-to-one reaction.

Pick the acid and base from lists that carry their proton counts, or set your own, then choose which of the four quantities you want to find. Alongside the answer the page reports moles and equivalents on each side, the equivalence volume, the salt that forms, and how much reagent is left over at the volumes you actually entered.

All the arithmetic happens in your browser and nothing is transmitted or stored. The page is also honest about the difference between the equivalence point and the endpoint your indicator shows, since those two only line up when the indicator is chosen to suit the titration.

Frequently asked questions

How do you calculate the concentration of an unknown acid from a titration?

Multiply the titrant's concentration by its volume and by the number of hydroxides it supplies, then divide by the acid's volume and its number of acidic protons. For a monoprotic acid against NaOH that simplifies to Ma = Mb x Vb / Va.

What is the difference between the equivalence point and the endpoint?

The equivalence point is where the moles of acid and base are chemically balanced. The endpoint is where your indicator changes colour. A well-chosen indicator puts them close together, but they are not the same thing and a poor choice can leave a real gap.

Why does a weak acid titration not end at pH 7?

The salt formed at equivalence is the conjugate base of a weak acid, and it pulls protons off water, pushing the pH above 7. That is why phenolphthalein, which changes colour around pH 8.2, suits weak acid titrations and methyl orange does not.

How do you handle a diprotic acid like sulfuric acid?

Count both of its protons. Choose sulfuric acid from the list and the tool uses n equal to 2, so one mole of it neutralises two moles of sodium hydroxide. Skipping that factor is the single most common source of a wrong titration answer.

What does the excess reagent figure tell me?

It compares the equivalents on each side at the exact volumes you typed and reports whatever is left over, plus its concentration in the combined volume. For a strong acid or base that leftover concentration is what sets the final pH.

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