Final answer:
Salts with cations that are the conjugate acid of a weak base and an anion from a strong acid are acidic because the cation can undergo acid hydrolysis, leading to an acidic solution.
Step-by-step explanation:
Salts that contain cations which are the conjugate acid of a weak base and an anion of a strong acid are acidic.
When such salts dissolve in water, the cations can undergo acid ionization (or acid hydrolysis). The ionization of these acidic cations, which are typically the conjugate partners of weak bases, yields hydrolysis reactions that produce acidic solutions. An example is ammonium chloride (NH4Cl), which dissociates in water to form ammonium ions (NH4+) and chloride ions (Cl-). Here, the ammonium ion is the conjugate acid of the weak base ammonia (NH3), and since the chloride ion is the conjugate base of the strong acid HCl, it does not react with water to have a significant effect on the acidity of the solution.
Therefore, the correct answer to the student's question is: a) acidic.