CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
Malonic acid, HOOC-CH₂-COOH (H₂A), is a diprotic acid with Ka1=1.5×10−3 and Ka2=2.0×10−6. A sample containing 50.0 mL of 0.100 M malonic acid is titrated with 0.200 M NaOH. Assume additive volumes.
(a) Write balanced net-ionic equations for the first and second neutralization reactions that occur during the titration.
(b) Calculate the volume (in mL) of NaOH required to reach the second equivalence point.
(c) Determine the molar concentration of the dianion A²⁻ in solution at the second equivalence point.
(d) Calculate the pH of the solution at the second equivalence point. Clearly indicate any approximations you make and verify their acceptability. Report the pH to two decimal places.