Which mixture would act as an acidic buffer?
Correct answer: D. Acetic acid and sodium acetate
- A. Hydrochloric acid and sodium chloride
- B. Sodium hydroxide and sodium chloride
- C. Ammonia and ammonium chloride
- D. Acetic acid and sodium acetate
Explanation
An acidic buffer needs a weak acid together with the salt of that acid, and acetic acid with sodium acetate is the standard example. Ammonia with ammonium chloride is also a buffer but a basic one, since it is built from a weak base and its salt, which is why it is the closest distractor. Hydrochloric acid is strong and fully ionised, so it has no reservoir of un-ionised acid and cannot buffer.
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About Buffer Solutions
Buffer solutions resist changes in pH when small amounts of acid or base are added, using a weak acid and its conjugate base or a weak base and its conjugate acid. Work includes buffer action, the common-ion effect, Henderson-Hasselbalch calculations, buffer capacity, and the difference between acidic and basic buffers.
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