Which of the following statements about ammonium salt is correct? It

Analyze the question: We need the true statement about ammonium salts (e.g., NH₄Cl, (NH₄)₂SO₄, NH₄NO₃).

Concept: Ammonium salts are soluble in water. The ammonium ion (NH₄⁺) is the conjugate acid of a weak base (NH₃), so it undergoes hydrolysis:

NH₄⁺ + H₂O ⇌ NH₃ + H₃O⁺

This produces H₃O⁺ ions, making the solution slightly acidic, with a pH below 7 (for salts of strong acids such as NH₄Cl).

Check each option:

• A. pH > 1: This is technically true for a typical ammonium salt solution (for example, pH is about 5 for NH₄Cl), but it is a vague and misleading statement. It would also be true of pure water and of alkaline solutions, so it does not describe the behavior of ammonium salts. It is not the best answer.
• B. pH < 7: Correct. The hydrolysis of NH₄⁺ gives an acidic solution.
• C. Does not decompose on heating: False. Ammonium salts decompose on heating. For example, NH₄Cl → NH₃ + HCl (it sublimes and dissociates), and NH₄NO₃ decomposes to N₂O and water.
• D. Insoluble in water: False. All common ammonium salts are soluble.

Answer: B.

Tip: Remember "salt of a strong acid and a weak base gives an acidic solution." Ammonium salts also all dissolve in water and all decompose on heating, and these two facts are often tested along with the pH.