Buffer pH and Composition (Henderson-Hasselbalch)
Buffer pH from a weak acid or base and its salt, or the composition for a target pH (Henderson-Hasselbalch).
Open the tool → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Buffer pair
- Weak acid and its salt
- What to work out
- pH from the two concentrations
- pKa at the working temperature
- 4.76
- pH mode: concentration of the salt (acid pair) or of the base
- 0.2 mol/L
- pH mode: concentration of the acid (acid pair) or of the salt
- 0.1 mol/L
Result: pH 5.06.
The tool opens with these values already filled in. Replace them with your own.
What you enter
- Buffer pair: a weak acid and its salt, or a weak base and its salt
- What to work out: the pH from two concentrations (ph), or the composition for a target pH (compose)
- pKa at the working temperature (for a weak base, of its conjugate acid)
- pH mode: concentration of the salt (acid pair) or of the base (base pair)
- pH mode: concentration of the acid (acid pair) or of the salt (base pair)
- Compose mode: target pH
- Compose mode: total buffer concentration
- Compose mode: volume, for grams (optional)
The other 2 fields
- Compose mode: molecular weight of the salt (acid pair) or of the base (base pair), for grams
- Compose mode: molecular weight of the acid (acid pair) or of the salt (base pair), for grams
How this is calculated
Citation
Physical chemistry: the mass-action expression for a weak acid in logarithmic form (the Henderson-Hasselbalch equation), pH = pKa + log10([salt] ÷ [acid]). The pKa is the reader's own figure; none is assumed.
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.