A student prepares two acetate buffer solutions, X and Y
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
A student prepares two acetate buffer solutions, X and Y, at 25 °C. Both buffers have a pH of 4.75. Solution X is 0.10 M in total acetate species, whereas solution Y is 1.0 M in total acetate species.
Acetic acid has a pKa of 4.76.
(1) Part 1: Compare quantitatively the ratios [CH3COO−]/[CH3COOH] in solutions X and Y. Justify your answer.
(2) Part 2: Identify which buffer has the greater capacity to resist a pH change upon addition of a strong acid. Explain your reasoning in terms of the chemical species present.
(3) Part 3: Predict qualitatively how the pH of each buffer will change, if at all, when the buffer is diluted twofold with distilled water. Provide an explanation based on equilibrium considerations.