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Question: Answered & Verified by Expert
A physician wishes to prepare a buffer solution at $p H=3.58$ that efficiently resists changes in $p H$ yet contains only small concentration of the buffering agents. Which of the following weak acids together with its sodium salt would be best to use
ChemistryIonic EquilibriumJEE Main
Options:
  • A $m$ - chlorgbenzoic acid $\left(p K_a=3.98\right)$
  • B $p$-chlorocionamic acid $\left(p K_a=4.41\right)$
  • C $2,5^{-}$ dihydroxy benzoic acid $\left(p K_a=2.97\right)$
  • D Acetoacetic acid $\left(p K_a=3.58\right)$
Solution:
2351 Upvotes Verified Answer
The correct answer is: $2,5^{-}$ dihydroxy benzoic acid $\left(p K_a=2.97\right)$
$p H=p K_a+\log \frac{[\text { Salt }]}{[\text { Acid }]}$. For small concentration of buffering agent and for maximum buffer gapacit $\frac{[\text {Salt }]}{[\text { Acid] }} \approx 1$.

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