The pH at the midpoint in the titration of an acid with a base is
A)equal to the pK of the corresponding acid.
B)equal to the pK of the corresponding base.
C)equal to 14 minus the pK of the corresponding acid.
D)equal to 14 plus the pK of the corresponding base.
E)none of the above

Question

Quizplus · Accepted Answer

The pH at the midpoint of a titration is equal to the pK of the acid being titrated. At the midpoint, the moles of acid and base are equal, and their conjugate acid-base pairs are in equal concentrations. Therefore, the equilibrium constant (Ka) for the acid is equal to the equilibrium constant (Kb) for the conjugate base, and their pK values are the same.

The PH at the Midpoint in the Titration of an Acid