Choosing a buffer for pH 7.4
Which conjugate acid–base pair would best resist pH changes in a closed laboratory solution at pH 7.4?
Answer A: explanation for every choice
A
Correct. Buffers work best within about ±1 pH unit of their pKa, and 7.2 is closest to 7.4.
B
Acetate buffers best around pH 3.8–5.8.
C
Ammonium buffers best around pH 8.3–10.3.
D
Bicarbonate works well in blood because the lungs remove CO2. In a closed solution, its pKa of 6.1 makes it a weaker choice at pH 7.4 than phosphate.
TakeawayChoose a buffer with pKa within about 1 unit of the target pH.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID cp134.