Identifying the Incorrectly Matched Option

This question asks which of the given options is incorrectly matched. Each option shows a pair: a chemical name and its formula. To solve this, we need to recall the correct chemical formulas for common compounds and identify which pair does not match.

Step-by-Step Analysis:

Step 1: Analyze Option 1

Option 1: "Calcium bicarbonate - Ca(HCO₃)₂"

Calcium has a valency of +2, and bicarbonate (HCO₃) has a valency of -1. The formula should be Ca(HCO₃)₂ to balance the charges. This is correctly matched.

Step 2: Analyze Option 2

Option 2: "Sodium zincate - Na₂ZnO₂"

Sodium zincate is formed when zinc reacts with sodium hydroxide. Its correct formula is Na₂ZnO₂. Sodium (Na⁺) has +1 charge, zincate (ZnO₂^2-) has -2 charge. So, Na₂ZnO₂ is correct. This is correctly matched.

Step 3: Analyze Option 3

Option 3: "Sodium plumbite - Na₂PbO₂"

Plumbite ion is PbO₂^2-. Sodium (Na⁺) has +1 charge. To balance, the formula should be Na₂PbO₂. This is the correct formula for sodium plumbite. This is correctly matched.

Step 4: Analyze Option 4

Option 4: "Aluminium carbide - Al₄C₄"

Aluminium has a valency of +3, and carbide (C) has a valency of -4. To balance the charges, the formula should be Al₄C₃, not Al₄C₄. The correct formula is Al₄C₃. Therefore, this is incorrectly matched.

Final Answer: The fourth option, "Aluminium carbide - Al₄C₄", is incorrectly matched. The correct formula for aluminium carbide is ${Al}_{4} C_{3}$ .

Related Topics:

Chemical Nomenclature
Valency and Chemical Formulas
Writing Formulas for Ionic Compounds
Common Polyatomic Ions

Important Formulae and Theory:

To write the formula of an ionic compound:

Identify the ions and their charges.
Use the criss-cross method to balance the charges.
Ensure the subscripts are in the simplest ratio.

Example: For aluminium carbide, Al³⁺ and C^4-. Criss-cross gives Al₄C₃.

Common ions:

Bicarbonate: HCO₃^-
Zincate: ZnO₂^2-
Plumbite: PbO₂^2-
Carbide: C^4-