The following substances are normal salts except

Analyze the question: We need to find the substance that is NOT a normal salt.

Concept:

• A normal salt forms when all the replaceable hydrogen ions (H⁺) of an acid are completely replaced by metal (or ammonium) ions. It contains no replaceable H⁺ and no OH⁻.
• An acid salt still has replaceable hydrogen (e.g., NaHSO₄, NaHCO₃).
• A basic salt contains hydroxide (OH⁻) or oxide in addition to the anion, which means the base was only partly neutralised (e.g., Mg(OH)NO₃, Zn(OH)Cl).

Checking each option:

• A. Al(NO₃)₃ is formed from Al(OH)₃ + 3HNO₃. All the OH⁻ and H⁺ are fully neutralised, so it is a normal salt.
• B. FeSO₄ is formed from Fe(OH)₂ + H₂SO₄. It contains only Fe²⁺ and SO₄²⁻, so it is a normal salt.
• C. Mg(OH)NO₃ contains Mg²⁺, OH⁻ and NO₃⁻. The Mg(OH)₂ base (which has two OH⁻) was only partially neutralised by HNO₃, leaving one OH⁻ behind: Mg(OH)₂ + HNO₃ → Mg(OH)NO₃ + H₂O This is a basic salt, not a normal salt.
• D. NaCl is formed from NaOH + HCl. It is a normal salt.

Answer: The exception is **C.

Tip: Look for leftover H in the formula (acid salt) or leftover OH (basic salt). If the formula contains only a metal and an acid radical, it is a normal salt.