Acid-Base Neutralization Calculator

Determine equivalence point, limiting reagent, and final pH for strong acid–strong base neutralization reactions.

Acid
Base
HCl + NaOH
Acetic Acid + NaOH
H₂SO₄ + NaOH
Excess Acid
Client-side only — no data uploaded.
Neutralization Analysis

⚡ Acid Equivalents: — mol

⚡ Base Equivalents: — mol

? Limiting Reagent: —

⚖️ Equivalence Status: —

? Total Volume: — L

?️ Final pH: —

pH Scale:
7.00
Titration Curve

The curve shows pH change as base is added. The steepest point indicates the equivalence point (calculated from 0 to 1.5×Veq).

Understanding Acid‑Base Neutralization

Neutralization is the reaction between H⁺ (from acid) and OH⁻ (from base) to form water. For strong acids and bases (e.g., HCl, NaOH), the reaction goes to completion.

Core principle: At the equivalence point, moles of H⁺ = moles of OH⁻.

Ca·Va·za = Cb·Vb·zb

where z is the number of H⁺/OH⁻ per formula unit.

Why is this useful?

  • Titration planning: Determine the volume of titrant needed to reach equivalence.
  • Buffer preparation: Estimate amounts for partial neutralization.
  • Industrial processes: Scale‑up of neutralization steps.
  • Educational: Visualize stoichiometric relationships.

pH after mixing (strong‑strong)

The final pH depends on which ion is in excess:

Condition Excess species pH calculation
n(H⁺) = n(OH⁻) None (neutral salt) pH = 7.00 (at 25°C)
n(H⁺) > n(OH⁻) H⁺ [H⁺] = excess mmol / total volume (mL) → pH = -log₁₀([H⁺])
n(H⁺) < n(OH⁻) OH⁻ [OH⁻] = excess mmol / total volume → pOH = -log₁₀([OH⁻]), pH = 14 - pOH

* Assumes complete dissociation and neglects activity coefficients. When excess concentration is below 10⁻⁷ M, water autoionization dominates and pH is set to 7.00.

Polyprotic acids & bases

Acids like H₂SO₄ can donate 2 H⁺ (za=2); bases like Ba(OH)₂ accept 2 H⁺ (zb=2). Our calculator handles this via the acidity/basicity input. For weak polyprotic species (e.g., H₃PO₄), the first equivalence point is still governed by stoichiometry, but the pH calculation requires more advanced treatment.

Calculator features at a glance:

  • Three modes: find base volume, find acid volume, or just calculate pH with both volumes known.
  • Accepts any positive concentration/volume and integer valence.
  • Visual bar comparison of H⁺ vs OH⁻ millimoles.
  • Estimates final pH (strong acid/base) with clear excess indication, neutral when excess < 1e-7 M.
  • Dynamic chart updates with every calculation.

Frequently Asked Questions

Using mL directly gives millimoles (mmol) when multiplied by concentration (mol/L). This avoids conversion factors and makes the numbers more readable.

The volume calculation (stoichiometry) remains correct even for weak acids/bases, because moles are conserved. However, the final pH estimate (based on complete dissociation) may differ; use it as an approximation only.

Set the "acidity" field to 2. The calculator will then use n(H⁺) = 2 × C × V. The same applies for bases: e.g., Ba(OH)₂ → basicity = 2.

The same formula applies: multiply concentration by volume by valence. The calculator automatically computes the required volume to reach the first equivalence point (all H⁺ neutralized).