About the pH Titration Buffer Calculator - Henderson-Hasselbalch Planning
Acid-base chemistry underpins biological systems, industrial processes, and analytical chemistry. pH is the most common metric — a logarithmic scale where each unit represents a 10× change in hydrogen ion concentration.
Key relationships
- pH = −log[H⁺]; pOH = −log[OH⁻]; pH + pOH = 14 at 25°C
- Henderson-Hasselbalch equation: pH = pKa + log([A⁻]/[HA]) — calculates buffer pH from the ratio of conjugate base to weak acid
- Titration equivalence point: where moles of acid = moles of base. For strong acid + strong base, equivalence point pH = 7. For weak acid + strong base, it's above 7.
Buffer design
Buffers work best within ±1 pH unit of the pKa of the weak acid used. Outside this range, the buffer capacity drops sharply. For a target pH of 7.4 (blood), phosphate (pKa 7.2) or HEPES (pKa 7.5) are commonly chosen.
Common mistakes
- Forgetting that pH is logarithmic: going from pH 7 to pH 5 is a 100× increase in [H⁺], not a 2-unit increase
- Using strong acid concentrations before equilibrium is established — strong acids fully dissociate, weak acids only partially
Helpful products for this plan
Practical items for lab prep, dilutions, and safer handling.