At 298 K, a certain buffer solution contains equal concentrations of X- and HX. Kb for X- is 10-10. What is the pH of this buffer solution?
- 10
- 4
- 2
- 6
Answer
(2) 4
Solution
Ka(HX) = KwKb(X-) = 10-1410-10 = 10-4
⇒ pKa = 4
For an acidic buffer (Henderson equation): pH = pKa + log [X-][HX]
∵ [X-] = [HX] ⇒ pH = 4 + log 1 = 4
Answer: (2)