An example of an acid salt is

The correct answer is (c) NaHSO₄. An acid salt is a salt that is derived from the partial neutralization of an acid, resulting in a substance that has both acidic and basic properties. NaHSO₄ is an example of an acid salt because it is derived from the partial neutralization of sulfuric acid (H₂SO₄) with sodium hydroxide (NaOH). It has acidic properties because it can donate a hydrogen ion (H+) in water, and it has basic properties because it can accept a hydrogen ion (H+) in the presence of a strong acid. The other options are not acid salts. CH₃COOONa is a salt of a weak acid (acetic acid) and a strong base (sodium hydroxide), and therefore it is a basic salt. Mg(OH)Cl is a salt of a strong base (magnesium hydroxide) and a strong acid (hydrochloric acid), and therefore it is a neutral salt. (NH₄)₂SO₄ is a salt of a weak base (ammonia) and a strong acid (sulfuric acid), and therefore it is an acidic salt.