* Hydrolysis: When ammonium chloride dissolves in water, it undergoes hydrolysis. This means the ammonium ion (NH₄⁺) reacts with water to form hydronium ions (H₃O⁺), which increase the acidity of the solution.

NH₄⁺ + H₂O ⇌ H₃O⁺ + NH₃

* Weak Base: Ammonia (NH₃) is a weak base. The ammonium ion is the conjugate acid of ammonia. Since ammonia is a weak base, its conjugate acid is relatively strong, making the solution acidic.

In summary: The hydrolysis of ammonium chloride produces hydronium ions, making the solution acidic.