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⚗️ Neutralization Calculator

Calculate the volume or concentration of acid or base needed for stoichiometric neutralization, accounting for polyprotic species.

Solve for:

Acid Concentration (M_acid) mol/L

Acid Basicity H⁺ per molecule, e.g. 1 for HCl, 2 for H₂SO₄

Acid Volume (V_acid) mL

Base Concentration (M_base) mol/L

Base Acidity OH⁻ per molecule, e.g. 1 for NaOH, 2 for Ca(OH)₂

Base Volume (V_base) mL

Result

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💡 Note: Basicity/acidity (valence) accounts for polyprotic acids and bases with multiple hydroxides — e.g. H₂SO₄ provides 2 H⁺ per molecule, Ca(OH)₂ provides 2 OH⁻ per molecule. Using valence=1 for both treats the reaction as simple 1:1 monoprotic neutralization.

📖 Example: 25 mL of 0.5 M HCl (valence 1) neutralized by 0.5 M NaOH (valence 1): N₁V₁=N₂V₂ → 0.5×25 = 0.5×V_base → V_base = 25 mL.

Frequently asked questions

Why does the calculator ask for 'valence' or basicity/acidity?

Neutralization depends on matching moles of H+ to moles of OH-, not just moles of acid to moles of base. A diprotic acid like H2SO4 releases 2 H+ per molecule, so 1 mole of H2SO4 neutralizes as much base as 2 moles of a monoprotic acid like HCl — the valence input accounts for this.

What does N1V1 = N2V2 mean?

This is the normality-based neutralization equation, where N (normality) equals molarity multiplied by valence (H+ or OH- per molecule). At the equivalence point, moles of H+ equal moles of OH-, which is exactly what N1V1 = N2V2 expresses when V is volume.

Does this calculator tell me the pH at the endpoint?

No — this calculates the stoichiometric volume or concentration needed to reach chemical equivalence (equal moles of H+ and OH-), not the resulting pH. For a strong acid/strong base reaction the endpoint pH is close to 7, but weak acid/weak base combinations can have an equivalence point pH significantly different from 7, which this simple stoichiometric calculator does not address.

Accuracy & how this is derived

Derivation: Standard normality-based neutralization equation: N1V1 = N2V2, where normality (N) equals molarity multiplied by the number of exchangeable H+ or OH- per molecule (valence/basicity/acidity), reflecting stoichiometric equivalence at the reaction endpoint.

Validated against: Fundamental acid-base stoichiometry used throughout analytical and general chemistry titration calculations.

⚠️ For educational and research support only — verify critical results independently before use in regulated, clinical, or publication-bound work.

✔ Last updated: July 2026 · Report an error

Stoichiometric acid-base neutralization calculations

Acid-base neutralization calculations determine the volume or concentration of one reagent needed to exactly react with a known amount of another, based on matching the total moles of available hydrogen ions from the acid to the total moles of available hydroxide ions from the base. For simple monoprotic acids and bases this reduces to matching moles of acid to moles of base directly, but polyprotic acids and bases with more than one exchangeable proton or hydroxide per molecule require an additional valence factor to correctly account for their greater neutralizing capacity per mole.