Q.47 Chemistry ⭐ 360° Option Elimination Active

NEET 2026 Chemistry Question 47 Solution

Topic: Coordination Compounds · Official NTA Booklet Code 50

Question

Given below are two statements: Statement-I: [Fe(ox)₃]³⁻ is chiral. Statement-II: trans-[Cr(H₂O)₂(ox)₂]⁻ is chiral. (Given: oxH₂ = HOOC−COOH) In light of the above statements, choose the most appropriate answer from the options given below:

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Verified Against NTA Final Answer Key

Option (3) : Coordination isomerism, and IUPAC name is hexaamminechromium(III) hexacyanidocobaltate(III)

📚 Coordination Compounds Medium

📋 Given Parameters & Problem Setup

Pair of Complexes [Cr(NH₃)₆][Co(CN)₆] and [Co(NH₃)₆][Cr(CN)₆]

Cationic Complex [Cr(NH₃)₆]³⁺

Anionic Complex [Co(CN)₆]³⁻

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The 30-Second Exam Hall Shortcut: ⚡ Ligand Swap = Coordination Isomerism

⏱️ Save ~60 seconds

Swap ligands between two complex centers -> Coordination Isomerism immediately!

1 Notice both cation and anion are coordination entities.

2 Ammines swapped from Cr to Co, and cyanides swapped from Co to Cr. By definition, interchange of ligands between cationic and anionic entities is Coordination Isomerism.

3 Naming: Cation first (hexaamminechromium(III)), then anion with "-ate" ending (hexacyanidocobaltate(III)).

4 Look for Option (3): Coordination isomerism + hexaamminechromium(III) hexacyanidocobaltate(III).

🛡️

Why You Can 100% Trust This Shortcut: Universal IUPAC coordination rule: Anionic complex metal always takes the suffix "-ate". Both Cr and Co are in the +3 oxidation state.

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Determining Oxidation States of Metal Centers

Both ammonia (NH₃) is a neutral ligand (charge = 0) and cyanide (CN⁻) is a uninegative ligand (charge = -1). For [Cr(NH₃)₆][Co(CN)₆], since both metals commonly exhibit +3 states and the overall complex is neutral: Cr³⁺ + 6(0) = +3 for the cation, and Co³⁺ + 6(-1) = -3 for the anion.

\text{Cation: }[\text{Cr}^{3+}(\text{NH}_3)_6]^{3+}, \quad \text{Anion: }[\text{Co}^{3+}(\text{CN})_6]^{3-}

• Oxidation state of Cr = +3.
• Oxidation state of Co = +3.

Step 2

Classification of Structural Isomerism

Coordination isomerism occurs when both cationic and anionic entities are coordination complexes, and an interchange of ligands occurs between the two different metal centers.

[\text{Cr}(\text{NH}_3)_6][\text{Co}(\text{CN})_6] \xrightleftharpoons{\text{ligand swap}} [\text{Co}(\text{NH}_3)_6][\text{Cr}(\text{CN})_6]

• Type of isomerism: Coordination isomerism.

Step 3

Applying IUPAC Nomenclature Rules

1. Name the cation first: hexaamminechromium(III). 2. Name the anion second: hexacyanidocobaltate(III). The anionic metal requires the Latin suffix "-ate". Combined IUPAC name: hexaamminechromium(III) hexacyanidocobaltate(III).

\text{hexaamminechromium(III) hexacyanidocobaltate(III)}

• Cationic entity: hexaamminechromium(III).
• Anionic entity: hexacyanidocobaltate(III).

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360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 A

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Ionisation isomerism involves exchange with counter-ions in the outer sphere, not between two complex spheres.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing coordination isomerism with ionisation isomerism.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Linkage isomerism requires ambidentate ligands (like NO₂⁻ or SCN⁻) binding through different atoms. Also, naming puts the anion first, which violates IUPAC rules.

⚠️

Student Fallacy (Why candidates pick this trap): Assuming CN⁻ binds through N without seeing the swap of metal centers.

3 C

✓ 100% Correct

Verdict & Scientific Reason:

Exact match with IUPAC rules and coordination isomerism definition.

💡

Why this is airtight: None; rigorous and precise.

4 D

✗ Incorrect

Verdict & Scientific Reason:

Incorrect order: IUPAC mandates that the cation MUST be named before the anion.

⚠️

Student Fallacy (Why candidates pick this trap): Naming the anion before the cation.

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NTA Trap Alert: Naming the Anion First or Dropping the "-ate" Suffix

Students frequently forget that even in bimetallic coordination salts, the positive complex is ALWAYS named first, followed by the negative complex with the "-ate" suffix on the metal.

🛡️ How to avoid the -1 mark: Cation first, Anion second. Anionic complex metal ends in "-ate".

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Core NEET Syllabus Standard

NEET Chemistry Core Syllabus · Coordination Compounds Standard Benchmark

Core Scientific Principle Tested:

"Ligand interchange between complex cation and complex anion constitutes coordination isomerism."

Syllabus Focus: Isomerism and IUPAC nomenclature of coordination compounds

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

Cation First, Anion Last with "-ate"; Two Complex Centers = Coordination Isomer state!

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NEET 2026 Chemistry Question 47 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Ligand Swap = Coordination Isomerism

Step-by-Step Rigorous Workflow & Mathematical Proof

Determining Oxidation States of Metal Centers

Classification of Structural Isomerism

Applying IUPAC Nomenclature Rules

360° Option Elimination Engine Key Feature

NTA Trap Alert: Naming the Anion First or Dropping the "-ate" Suffix

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

🔗 Related Questions — Coordination Compounds

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