Dont need calculations for this problem, just this answer: What accounts for the difference in the hydronium ion concentrations? Explain this based on equilibrium concepts; in other words, saying that "one solution is a buffer" is not sufficient.
One beaker contains 10.0 mL of acetic acid/sodium acetate buffer at maximum buffer capacity (equal concentrations of acetic acid and sodium acetate), and another contains 10.0 mL of pure water. Calculate the hydronium ion concentration and the pH after the addition of 0.25 mL of 0.10 M HCl to each one. Ka of acetic acid = 1.8 x 10-5 Acetic acid/sodium acetate buffer Acetic acid .1M Sodium acetate .1M