Final answer:
The question involves calculating the pH of a buffer solution using the Henderson-Hasselbalch equation. The correct pH of the given buffered solution containing 0.20 M acetic acid and 0.40 M sodium acetate is approximately 5.04, which is not among the provided answer options.
Step-by-step explanation:
The question is asking for the pH of a solution consisting of 0.20 M acetic acid (CH3COOH) and 0.40 M sodium acetate (NaCH3COO). The solution represents a buffer system, which is a mixture of a weak acid and its conjugate base. Given the acid dissociation constant (Ka) for acetic acid is 1.8 x 10-5, we can use the Henderson-Hasselbalch equation to calculate the pH of the buffered solution:
pH = pKa + log([A-]/[HA])
Where pKa is the negative logarithm of the acid dissociation constant, [A-] is the concentration of the conjugate base, and [HA] is the concentration of the acid. Inserting the given values and Ka into the equation, we have:
pH = -log(1.8 x 10-5) + log(0.40/0.20)
pH = 4.74 + log(2)
pH = 4.74 + 0.301
pH = 5.041
Therefore, none of the provided options (pH 2.00, pH 2.50, pH 3.00, or pH 3.50) are correct. The pH of the solution is approximately 5.04.