What is the correct relation between pH and pKa?
Correct answer: D. pH = pKa + log[ Base/Acid ]
- A. pH = pKa + log[ Acid/Base ]
- B. pH = pKa - log[ Acid/Base ]
- C. pH = pKa - log[ Base/Acid ]
- D. pH = pKa + log[ Base/Acid ]
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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About Acids, Bases and Salts
Acid and base behaviour is explained through the Bronsted-Lowry transfer of protons and the Lewis donation or acceptance of electron pairs. The topic includes pH, pOH, ionisation and water equilibrium, plus salt formation and hydrolysis, where a salt solution may become acidic, basic or neutral.
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