Question

Mark each of the following statements about the ½ equivalence point of an acid-base titration TRUE or FALSE.

a. It is the point in the titration when the concentration of weak acid (HA) being titrated is equal to the concentration of the conjugate base (A− ).

b. It is the point halfway between the beginning of the titration of a weak acid or weak base and the equivalence point. 2

c. When a strong acid is titrated with a strong base, the pH at the half-equivalence point is equal to the pKa of the strong acid.

d. When a weak acid is titrated with a strong base, the pH at the half-equivalence point is equal to the pKa of the weak acid

Answer 1

a) True. During the titration of a weak acid (HA) with a strong base at half equivalence point half of the acid converts into salt(or) conjugate base.so that, both components have the same no of moles, concentration.

b) True. yes, it is exactly at the middle of the titration.

c) False.

d) True. pH = pka + log(conjugate base / weak acid)

if [conjugate base] = [weak acid]

pH = pka of weak acid.