What is the correct relation between pH and pKa?

Correct answer: B. pH = pKa - log[ Acid/Base ]

  • A. pH = pKa + log[ Acid/Base ]
  • B. pH = pKa - log[ Acid/Base ]
  • C. pH = pKa - log[ Base/Acid ]
  • D. pH = pKa + log[ Base]

Explanation

The Henderson-Hasselbalch equation relates pKa and pH. However, it is only an approximation and should not be used for concentrated solutions or for extremely low pH acids or high pH bases.pH = pKa + log ([conjugate base]/[weak acid])pH = pka + log ([A-] / [HA])pH is equal to the sum of the pKa value and the log of the conjugate base concentration divided by the weak acid concentration.

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