Which is a characteristic of weak acids and weak bases?
a. ka and kb values of weak acids and weak bases are small.
b. forward reactions of weak acids and weak bases are favored.
c. dissociation of weak acids and weak bases is nearly complete.
d. many h+ or oh– ions are present in their solution.

The correct answer is A: Ka and Kb values of weak acids and weak bases are small.

Explanation:

Weak acids dissociate incompletely; that is, if this weak acid is in solution of the HA form, then a significant amount of undissociated HA would be present in the aqueous solution formed.

Dissociation reaction of a weak acid:

⇔

The reaction constant is given by:

If [HA] concentration is high in the solution, that means that the denominator is bigger than the numerator and Ka is small.

Weak bases do not have too much capacity to capture protons, so the dissociation of water is partial and the concentration of base without dissociating in solution is high.

Dissociation reaction of a weak base:

⇔

The reaction constant is given by:

If [B] concentration is high in the solution, that means that the denominator is bigger than the numerator and Kb is small.