What is the pH of a solution made by dissolving 2.16 g of sodium benzoate (NaC₆H₅CO₂)in a sufficient volume of 0.033 M aqueous benzoic acid solution to prepare 500.0 mL of buffer? [K_a for benzoic acid is 6.3 × 10^-5] A)4.16 B)4.37 C)4.64 D)5.77 E)6.30

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Quizplus · Accepted Answer

The correct answer is A because the pH of a buffer solution can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]), where pKa is the dissociation constant of the weak acid, [A-] is the concentration of the conjugate base, and [HA] is the concentration of the weak acid. In this case, the pKa of benzoic acid is 6.3 × 10-5, and the concentration of the conjugate base (sodium benzoate) is 2.16 g / (144.11 g/mol) / 500.0 mL = 0.030 M. The concentration of the weak acid (benzoic acid) is 0.033 M. Substituting these values into the Henderson-Hasselbalch equation, we get: pH = 6.3 × 10-5 + log(0.030 / 0.033) = 4.16.

What Is the PH of a Solution Made by Dissolving