A teacher prepares two citrate buffers, Buffer A and Buffer B
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
A teacher prepares two citrate buffers, Buffer A and Buffer B, both initially at pH 3.20. Buffer A contains 0.10 M citric acid and 0.10 M sodium citrate. Buffer B contains 0.20 M citric acid and 0.20 M sodium citrate. No other components are present, and temperature is held constant at 25 °C.
(a) Explain why both buffers have the same initial pH even though their component concentrations differ.
(b) A small amount of strong base is added to each buffer. Describe qualitatively which buffer resists the pH change more effectively and explain the chemical reason for this behavior.
(c) Suppose instead that equal moles of strong acid are added to each buffer. Predict which buffer experiences the larger pH drop and justify your reasoning in terms of buffer capacity.
(d) Discuss how changing the ratio of acid to base (while keeping total concentration fixed) would alter a buffer’s ability to neutralize added base versus added acid.