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Buffer pH After Adding Strong Acid (Henderson–Hasselbalch) Calculator

How buffer pH shifts when strong acid is added.

Calculates the pH of a buffer after a known amount of strong acid is added, using the Henderson–Hasselbalch equation: pH = pKa + log([A−]/[HA]) with updated concentrations.

Dr. Helena Ortiz By Dr. Helena Ortiz
Published Last reviewed 1 min read

Inputs

mol
mol
mol

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

pH = pKa + log([A⁻]−n_acid / [HA]+n_acid)

In depth

Calculates the pH of a buffer after a known amount of strong acid is added, using the Henderson–Hasselbalch equation: pH = pKa + log([A−]/[HA]) with updated concentrations.