During the titration of 50.0 mL of 0.100 M acetic acid, CH₃COOH
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
During the titration of 50.0 mL of 0.100 M acetic acid, CH₃COOH, with 0.100 M NaOH, a student observes that after 15.0 mL of NaOH have been added (well before the equivalence point) the pH is 4.74. Answer the following questions about the system at this stage of the titration.
(a) Write the balanced net-ionic equation for the reaction occurring between the titrant and the analyte at this point in the titration.
(b) Identify the two conjugate species present in appreciable amounts that control the pH of the mixture at this point.
(c) Using principles of chemical equilibrium, explain clearly why the pH changes only gradually with small additions of base in this region of the titration curve.
(d) Predict qualitatively how the ability of the solution to resist pH change at this point would be affected if the initial concentration of acetic acid had been 0.050 M instead of 0.100 M. Justify your prediction.