NEET The d- and f-Block Elements & Group 17 Elements PYQs with Solutions

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Verified Against NTA Final Answer Key

Option (4) : Statement-I is incorrect but Statement-II is correct.

📚 The d- and f-Block Elements & Group 17 Elements Medium

📋 Given Parameters & Problem Setup

Statement-I Heating NaCl with concentrated H₂SO₄ and MnO₂ results in oxidation of Mn.

Statement-II Heating NaI with concentrated H₂SO₄ and MnO₂ results in reduction of Mn.

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The 30-Second Exam Hall Shortcut: ⚡ MnO₂ is an OXIDIZING Agent (It gets REDUCED!)

⏱️ Save ~50 seconds

MnO₂ oxidizes halides (Cl⁻/I⁻) to halogens, so Mn(+4) is REDUCED to Mn(+2) in BOTH cases!

1 Identify reagent role: MnO₂ (pyrolusite) is an oxidizing agent.

2 In both reactions with halides in acid: Halide is oxidized (2X⁻ → X₂ + 2e⁻).

3 Therefore, Manganese MUST be REDUCED (Mn⁺⁴ in MnO₂ → Mn⁺² in MnSO₄).

4 Statement-I claims "oxidation of Mn" -> FALSE! (Mn is reduced, not oxidized).

5 Statement-II claims "reduction of Mn" -> TRUE! (Mn is reduced to +2).

6 Statement-I is incorrect but Statement-II is correct -> Option (4) immediately!

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Why You Can 100% Trust This Shortcut: Fundamental redox principle: In any redox reaction, the oxidizing agent undergoes reduction. MnO₂ is the oxidizing agent and is reduced from +4 to +2.

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Analyze Statement-I (Reaction with NaCl)

Laboratory preparation of chlorine gas involves heating sodium chloride with concentrated sulfuric acid and manganese dioxide:

4\text{NaCl} + \text{MnO}_2 + 4\text{H}_2\text{SO}_4 \longrightarrow \text{MnSO}_4 + 2\text{NaHSO}_4 + 2\text{H}_2\text{O} + \text{Cl}_2\uparrow

• Chloride (Cl⁻) is oxidized from -1 to 0 (in Cl₂).
• Manganese in MnO₂ has oxidation state +4.
• Manganese in MnSO₄ has oxidation state +2.
• Because the oxidation number of Mn decreases from +4 to +2, Manganese undergoes REDUCTION, NOT oxidation!
• Statement-I is incorrect.

Step 2

Analyze Statement-II (Reaction with NaI)

Similarly, heating sodium iodide with concentrated sulfuric acid and manganese dioxide produces iodine vapor:

2\text{NaI} + \text{MnO}_2 + 2\text{H}_2\text{SO}_4 \longrightarrow \text{MnSO}_4 + \text{Na}_2\text{SO}_4 + 2\text{H}_2\text{O} + \text{I}_2\uparrow

• Iodide (I⁻) is oxidized from -1 to 0 (in I₂).
• Manganese is reduced from +4 (in MnO₂) to +2 (in MnSO₄).
• Because Mn gains electrons and its oxidation state decreases, Manganese undergoes REDUCTION.
• Statement-II is correct.

Step 3

Conclusion

Statement-I is incorrect, but Statement-II is correct.

\text{Statement-I: False} \quad (\text{Mn is reduced, not oxidized}), \quad \text{Statement-II: True}

• Matches Option (4).

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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. Statement-I falsely asserts that Mn is oxidized.

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Student Fallacy (Why candidates pick this trap): Confusing the substance being oxidized (Cl⁻) with the reagent causing the oxidation (MnO₂).

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Statement-II is factually correct (Mn is indeed reduced).

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Student Fallacy (Why candidates pick this trap): Thinking Mn undergoes no redox change.

3 C

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Exactly backwards.

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Student Fallacy (Why candidates pick this trap): Inverting the redox definitions of oxidation and reduction.

4 D

✓ 100% Correct

Verdict & Scientific Reason:

Scientifically rigorous: Mn undergoes reduction (+4 to +2) in both reactions, making Statement-I false and Statement-II true.

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Why this is airtight: None; flawless tracking of oxidation numbers.

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NTA Trap Alert: Confusing "Oxidizing Agent" with "Undergoing Oxidation"

A classic linguistic trap: students read "MnO₂ oxidizes NaCl" and mistakenly jump to the conclusion that "Mn is oxidized". An oxidizing agent is REDUCED during the reaction!

🛡️ How to avoid the -1 mark: Always assign oxidation states: Mn in MnO₂ is +4; Mn in MnSO₄ is +2. A drop in oxidation number is REDUCTION.

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Core NEET Syllabus Standard

NEET Chemistry Core Syllabus · The d- and f-Block Elements & p-Block Elements Standard Benchmark

Core Scientific Principle Tested:

"MnO₂ acts as an oxidizing agent in acidic solution, reducing from Mn(IV) to Mn(II)."

Syllabus Focus: Oxidizing properties of MnO₂ and preparation of halogens

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

MnO₂ oxidizes the halide crew; Mn itself is reduced from +4 to +2!

NEET The d- and f-Block Elements & Group 17 Elements Previous Year Questions with Solutions

The 30-Second Exam Hall Shortcut: ⚡ MnO₂ is an OXIDIZING Agent (It gets REDUCED!)

Step-by-Step Rigorous Workflow & Mathematical Proof

Analyze Statement-I (Reaction with NaCl)

Analyze Statement-II (Reaction with NaI)

Conclusion

360° Option Elimination Engine Key Feature

NTA Trap Alert: Confusing "Oxidizing Agent" with "Undergoing Oxidation"

Core NEET Syllabus Standard

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