In a buffer made of a weak acid HA and its conjugate base A-, what is the pH when [A-] equals [HA]?
Answer and explanation
Correct answer: C. It equals the pKa
- Step 1: The Henderson-Hasselbalch equation is pH = pKa + log([A-]/[HA]). Step 2. If the ratio is 1, the log is zero and pH = pKa. Answer: the pKa. Why not the others: 7 is neutral and does not depend on the buffer.
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