Which is the best choice for preparing a buffer with a pH of 3.5? A) C₅H₅O₅COOH, K_a = 4.0 × 10^-6 B) HOC₆H₄OCOOH, K_a = 1.0 × 10^-3 C) HBrO, K_a = 2.3 × 10^-9 D) C₆H₄(COOH)₂, K_a = 2.9 × 10^-4 E) CH₃COOH, K_a = 1.8 ×10^-5

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Quizplus · Accepted Answer

The best choice for preparing a buffer with a pH of 3.5 is the one whose acid dissociation constant (Ka) is closest to the hydrogen ion concentration corresponding to that pH. The pKa (which is the negative logarithm of Ka) should be close to the desired pH for optimal buffering capacity. Option D, with a pKa of 3.54 (since pKa = -log(2.9 × 10^-4)), is closest to the desired pH of 3.5, making it the best choice for a buffer at this pH.

Which Is the Best Choice for Preparing a Buffer with a PH