Why do the two solutions NaCl and CH3COOH have initially different pH values in a buffer solution experiment?

NaCl dissociates to form Na+ and Cl- ions, which do not affect pH since they are neutral species. On the other hand, CH3COOH is a weak acid that partially dissociates in water to form H+ ions, leading to a decrease in pH. This difference in the behavior of the two solutions causes them to have initially different pH values in a buffer solution experiment.