CHEMISTRY · Single correct · A Level · Chemistry · Acids and bases · Acids and bases
Problem
The triprotic acid H₃A has pKa values 2.10, 2.30, and 9.50. When a solution of this acid is titrated with 0.100 M KOH, which prediction about the titration curve is most accurate?
(a) Three distinct equivalence points will be visible since each proton neutralizes separately.
(b) Two equivalence points will be visible because the last two protons titrate together owing to the large difference between their pK_a values.
(c) Two distinct equivalence points will appear because the first two protons have nearly identical pK_a values, causing their titrations to merge.
(d) An initial equivalence point will occur at a pH near 2.2 followed by a second around 9.5, since equivalence points coincide with pK_a values.