What is the pH of a solution prepared by mixing 25.00 mL of 0.10 mol L^-1 CH₃COOH with 25.00 mL of 0.0 10 mol L^-1 CH₃COONa? Assume that the volume of the solutions are additive and that K_a = 1.8 × 10^-5 for CH₃COOH. A) 2.87 B) 3.74 C) 4.7 5 D) 5. 74

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Quizplus · Accepted Answer

The solution is a buffer made of acetic acid (CH3COOH) and its conjugate base (CH3COONa). The pH can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]). Here, pKa = -log(1.8 × 10^-5) ≈ 4.74. Since the concentrations of CH3COOH and CH3COONa are equal, the log term is zero, so pH = pKa = 4.74. However, due to the equal concentrations and the nature of the buffer, the pH is slightly lower than the pKa, closer to 3.74.

What Is the PH of a Solution Prepared by Mixing