Q.62 Chemistry ⭐ 360° Option Elimination Active

NEET 2025 Chemistry Question 62 Solution

Topic: Chemical Bonding and Molecular Structure · Official NTA Booklet Code 45

Question

Given below are two statements: Statement I: A hypothetical diatomic molecule with bond order zero is quite stable. Statement II: As bond order increases, the bond length increases. In the light of the above statements, choose the most appropriate answer from the options given below:

(1)Both Statement I and Statement II are true
(2)Both Statement I and Statement II are false
(3)Statement I is true but Statement II is false
(4)Statement I is false but Statement II is true

✓

Verified Against NTA Final Answer Key

Option (2) : Both Statement I and Statement II are false

📚 Chemical Bonding and Molecular Structure Easy

📋 Given Parameters & Problem Setup

Statement I A hypothetical diatomic molecule with bond order zero is quite stable.

Statement II As bond order increases, the bond length increases.

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The 30-Second Exam Hall Shortcut: ⚡ MOT Fundamental Axioms Check

⏱️ Save ~30 seconds

Bond order zero means NO net bonding forces ⟹ molecule DOES NOT EXIST (unstable)! Bond order increases (single → double → triple) ⟹ atoms pulled CLOSER ⟹ bond length DECREASES! Both statements are completely FALSE!

1 Examine Statement I: Bond Order = (N_b - N_a)/2. A bond order of zero means bonding electrons equal antibonding electrons (net attraction = 0). Such molecules (like He₂ or Be₂) are unstable and do not exist under normal conditions. Statement I claims it is "quite stable" ⟹ FALSE!

2 Examine Statement II: Greater bond order means more electron density shared between nuclei, pulling nuclei closer together (e.g., C-C = 154 pm, C=C = 134 pm, C≡C = 120 pm). Bond length DECREASES as bond order increases. Statement II claims bond length increases ⟹ FALSE!

3 Conclusion: Both Statement I and Statement II are false.

4 Match Option (2) in under 10 seconds!

🛡️

Why You Can 100% Trust This Shortcut: Molecular Orbital Theory & Bond Order Principles (NCERT Chemistry · Chemical Bonding and Molecular Structure: Bond Order = ½(N_b - N_a)).

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Evaluate Statement I (Significance of Bond Order Zero)

In Molecular Orbital Theory, the bond order is defined as half the difference between the number of bonding electrons (N_b) and antibonding electrons (N_a):

\text{Bond Order (B.O.)} = \frac{N_b - N_a}{2}

• A positive bond order (B.O. > 0) indicates a stable molecule.
• If B.O. = 0 (N_b = N_a), the antibonding destabilization completely cancels the bonding stabilization.
• The molecule cannot hold together and is unstable or non-existent (e.g., He₂, Be₂).
• Therefore, Statement I is unequivocally FALSE.

Step 2

Evaluate Statement II (Bond Order vs. Bond Length Relationship)

Bond order reflects the multiplicity of the covalent bond between two atoms:

\text{Bond Length} \propto \frac{1}{\text{Bond Order}}

• For carbon-carbon bonds: C-C (B.O. = 1, length = 154 pm), C=C (B.O. = 2, length = 134 pm), C≡C (B.O. = 3, length = 120 pm).
• As bond order increases, bond length DECREASES, and bond dissociation enthalpy increases.
• Statement II states that bond length increases, which is completely FALSE.

Step 3

Select Matching Option

Since both statements are false, select Option (2).

\text{Statement I: False}, \quad \text{Statement II: False} \implies \text{Option (2)}

• Matches Option (2) with complete scientific accuracy.

⭐

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. Both statements contradict fundamental MOT laws.

⚠️

Student Fallacy (Why candidates pick this trap): Total misconception of bond order.

2 B

✓ 100% Correct

Verdict & Scientific Reason:

100% correct. B.O. = 0 means unstable/non-existent, and higher B.O. shortens bond length.

💡

Why this is airtight: None; solid conceptual grasp of chemical bonding.

3 C

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Statement I is false.

⚠️

Student Fallacy (Why candidates pick this trap): Believing B.O. = 0 can be stable.

4 D

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Statement II is false.

⚠️

Student Fallacy (Why candidates pick this trap): Thinking higher bond order increases bond length.

⚠️

NTA Trap Alert: Confusing Bond Energy with Bond Length

As bond order increases, bond STRENGTH and bond ENERGY increase, but bond LENGTH decreases! Candidates who confuse bond length with bond energy mistakenly believe Statement II is true.

🛡️ How to avoid the -1 mark: Triple bond is STRONGER but SHORTER: Bond order up ⟹ Bond length down!

📖

Core NEET Syllabus Standard

NEET Chemistry Core Syllabus · Chemical Bonding and Molecular Structure Standard Benchmark

Core Scientific Principle Tested:

"B.O. = 0 means unstable molecule; Bond length is inversely proportional to bond order."

Syllabus Focus: Molecular Orbital Theory & Bond Parameters

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

B.O. = 0 is unstable, higher B.O. shrinks the bond ⟹ Both statements are FALSE!

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NEET 2025 Chemistry Question 62 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ MOT Fundamental Axioms Check

Step-by-Step Rigorous Workflow & Mathematical Proof

Evaluate Statement I (Significance of Bond Order Zero)

Evaluate Statement II (Bond Order vs. Bond Length Relationship)

Select Matching Option

360° Option Elimination Engine Key Feature

NTA Trap Alert: Confusing Bond Energy with Bond Length

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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