Two acetic acid/acetate buffer solutions are prepared at 25 °C (pK_a = 4.76)
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
Two acetic acid/acetate buffer solutions are prepared at 25 °C (pK_a = 4.76).
• Buffer X: 0.10 M CH₃COOH and 0.10 M CH₃COONa, 100 mL total volume
• Buffer Y: 1.00 M CH₃COOH and 1.00 M CH₃COONa, 100 mL total volume
Each buffer is challenged with 0.010 mol of solid NaOH, which dissolves instantaneously. Assume temperature and volume remain constant.
(a) Calculate the initial pH of Buffer X and Buffer Y before NaOH is added.
(b) Determine the pH of each buffer after the 0.010 mol NaOH addition.
(c) Using your results, quantify which buffer possesses the greater buffer capacity, and by what factor (expressed as the ratio of pH changes).
(d) Provide a molecular-level explanation for how absolute concentration affects buffer capacity, even when the ratio of conjugate base to acid is identical.