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How does hydrolysis cause some salt solutions to become acidic or basic?

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sodium sulfate — acid–base reaction Sodium sulfate, also called Glauber's salt, is, like other salts, the product of an acid-base reaction.

In chemistry, the hydrolysis of salts refers to the process where salt solutions exhibit acidic or basic properties due to the interaction of their constituent ions with water. Under the Brønsted–Lowry concept, this occurs as a natural consequence of proton-transfer reactions.1

Basic Solutions: When a salt derived from a weak acid and a strong base (such as sodium acetate) dissolves, the anion acts as a base by accepting a proton from water. This reaction produces hydroxide ions (OH⁻), which increases the basicity of the solution.12
Acidic Solutions: Salts derived from a weak base and a strong acid (such as ammonium chloride) produce acidic solutions because the cation acts as an acid, donating a proton to water to form hydronium ions (H₃O⁺).1
Metal Salts: Salts containing multiply charged metal cations (e.g., aluminum or ferric salts) also form acidic solutions. These cations are strongly hydrated in water; a proton is transferred from a water molecule in the hydration shell to the solvent, generating hydronium ions.1