A buffer solution is prepared by dissolving benzoic acid (C₆H₅COOH) and sodium…
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
A buffer solution is prepared by dissolving benzoic acid (C₆H₅COOH) and sodium benzoate (C₆H₅COONa) in water so that the final concentrations are 0.200 M benzoic acid and 0.050 M sodium benzoate. The temperature is held constant at 25 °C. A calibrated pH electrode placed in the solution reads 3.62.
(a) Calculate the numerical value of [C6H5COOH][C6H5COO−] in the buffer.
(b) Determine the acid-dissociation constant, Kₐ, and the pKₐ of benzoic acid at 25 °C based on the experimental pH value.
(c) The literature pKₐ of benzoic acid at 25 °C is 4.20. Calculate the percent error of the experimental pKₐ obtained in part (b).