How to Calculate Henderson-Hasselbalch
What is Henderson-Hasselbalch?
The Henderson-Hasselbalch equation calculates the pH of a buffer solution containing a weak acid and its conjugate base. pH = pKa + log([A⁻]/[HA]). It is fundamental in biochemistry for maintaining physiological pH.
Step-by-Step Guide
- 1Identify the weak acid (HA) and its conjugate base (A⁻)
- 2Find or calculate pKa = −log(Ka)
- 3Measure concentrations [HA] and [A⁻]
- 4pH = pKa + log([A⁻]/[HA])
Worked Examples
Input
Acetic acid pKa=4.76 · [CH₃COO⁻]=0.1M · [CH₃COOH]=0.1M
Result
pH = 4.76
Equal concentrations → log(1)=0 → pH=pKa
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