Which pair can act as an acidic buffer in water?

A) HCl and NaCl

B) NaOH and NaCl

C) HNO₃ and KNO₃

D) CH₃COOH and CH₃COONa

Answer: D

Explanation: Acetic acid is a weak acid and sodium acetate supplies its conjugate base. Together they resist large pH changes when modest acid or base is added.

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