A 25.0 mL sample of an aqueous solution of a diprotic acid H₂B is titrated with 0.150…
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
A 25.0 mL sample of an aqueous solution of a diprotic acid H₂B is titrated with 0.150 M KOH. The first equivalence point is reached after exactly 33.3 mL of base has been delivered. The acid-dissociation constants are Ka1=1.2×10−3 and Ka2=7.5×10−8 at 25 °C.
Answer the following.
(a) Calculate the initial molarity of H₂B in the sample.
(b) Determine the pH of the solution after exactly 16.7 mL of KOH has been added.
(c) Explain whether the second deprotonation step of the acid has any significant impact on the pH calculated in part (b).