Is Your Henderson–Hasselbalch Calculation of Buffer pH Correct?

• Charles A. Lucy ^[1]
  1. [1] University of Alberta

     University of Alberta

     Canadá

     
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 100, Nº 6, 2023, págs. 2418-2422
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • A survey of 21 free online buffer calculators and apps found only 2 that correctly calculated pH under conditions where [H+] and [OH–] cannot be ignored in the ratio term of the Henderson–Hasselbalch equation. Traditional guidelines for when use of formal concentrations is acceptable were found to be flawed. For acidic (pKa ≤ 7) buffers, the use of formal concentrations is valid when FA–/Ka > 20. For alkaline (pKa ≥ 7) buffers, the approximation is valid when FBH+/Kb > 20. Robust equations for predicting pH of acidic and alkaline buffers are presented, which could be used with programmable calculators and should be used for online buffer calculators and apps.