A technician compares the effect of a strong base on
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
A technician compares the effect of a strong base on (i) pure water and (ii) an aqueous buffer composed of 0.050 M formic acid and 0.050 M sodium formate (pK_a = 3.75). In each case, 0.0010 mol of NaOH is added to 1.00 L of solution at 25 °C.
(a) Calculate the pH of pure water after the NaOH addition.
(b) Calculate the pH of the buffer solution after the NaOH addition, assuming the added volume is negligible.
(c) Using your numerical results, explain in words why the unbuffered solution exhibits a much larger pH change than the buffered solution. In your explanation, discuss the roles of both the [A−]/[HA] ratio and the presence of a conjugate acid–base pair.