Q.86 Chemistry ⭐ 360° Option Elimination Active

NEET 2023 Chemistry Question 86 Solution

Topic: The p-Block Elements · Official NTA Booklet Code G5

Question

Match List - I (Oxoacids of Sulphur) with List - II (Bonds): List I: A. Peroxodisulphuric acid; B. Sulphuric acid; C. Pyrosulphuric acid; D. Sulphurous acid. List II: I. Two S-OH, Four S=O, One S-O-S; II. Two S-OH, One S=O; III. Two S-OH, Four S=O, One S-O-O-S; IV. Two S-OH, Two S=O. Choose the correct answer from the options given below:

✓

Verified Against NTA Final Answer Key

Option (3) : A-III, B-IV, C-I, D-II

📚 The p-Block Elements Medium

📋 Given Parameters & Problem Setup

Oxoacids (List I) A. Peroxodisulphuric acid, B. Sulphuric acid, C. Pyrosulphuric acid, D. Sulphurous acid

Bond descriptions (List II) I. Two S-OH, Four S=O, One S-O-S; II. Two S-OH, One S=O; III. Two S-OH, Four S=O, One S-O-O-S; IV. Two S-OH, Two S=O

⚡

The 30-Second Exam Hall Shortcut: ⚡ Peroxo Bridge Scan: Marshall’s Acid (H₂S₂O₈) Uniquely Contains S–O–O–S Bridge (A → III)

⏱️ Save ~35 seconds

Peroxodisulphuric acid (H₂S₂O₈) has a peroxo bridge (S–O–O–S) → A-III. This immediately eliminates Options (2) and (4). Pyrosulphuric acid (Oleum, H₂S₂O₇) has an S–O–S bridge → C-I. Matches Option (3) uniquely: A-III, B-IV, C-I, D-II in 10 seconds!

1 Match A (Peroxodisulphuric acid, H₂S₂O₈): Must contain peroxo linkage S–O–O–S → III.

2 Match B (Sulphuric acid, H₂SO₄): O=S(=O)(OH)₂ has two S=O and two S–OH → IV.

3 Match C (Pyrosulphuric acid / Oleum, H₂S₂O₇): Contains bridging S–O–S, four S=O, two S–OH → I.

4 Match D (Sulphurous acid, H₂SO₃): O=S(OH)₂ has one S=O and two S–OH → II.

5 Complete combination: A-III, B-IV, C-I, D-II (Option 3).

🛡️

Why You Can 100% Trust This Shortcut: Standard NCERT Group 16 Oxoacids of Sulphur structural diagram.

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Structure of Peroxodisulphuric Acid (H₂S₂O₈)

Known as Marshall’s acid, each sulphur is in oxidation state +6 and is bonded to one -OH, two =O, and joined by a peroxo linkage:

\text{HO}-\text{SO}_2-\text{O}-\text{O}-\text{SO}_2-\text{OH} \implies \text{Two S-OH, Four S=O, One S-O-O-S (III)}

Step 2

Structure of Sulphuric Acid (H₂SO₄)

Sulphur is surrounded by four oxygen atoms in a tetrahedral geometry:

\text{O}=\text{S}(=\text{O})(\text{OH})_2 \implies \text{Two S-OH, Two S=O (IV)}

Step 3

Structure of Pyrosulphuric Acid (H₂S₂O₇)

Also known as oleum, formed by condensing two molecules of sulphuric acid with elimination of water:

\text{HO}-\text{SO}_2-\text{O}-\text{SO}_2-\text{OH} \implies \text{Two S-OH, Four S=O, One S-O-S (I)}

Step 4

Structure of Sulphurous Acid (H₂SO₃)

Sulphur has one lone pair, with oxidation state +4:

\text{O}=\text{S}(\text{OH})_2 \implies \text{Two S-OH, One S=O (II)}

⭐

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 (1)

✗ Incorrect

Verdict & Scientific Reason:

Mismatches pyrosulphuric acid with sulphurous acid.

⚠️

Student Fallacy (Why candidates pick this trap): Candidate confused the pyrosulphuric S-O-S bridge with sulphurous acid.

2 (2)

✗ Incorrect

Verdict & Scientific Reason:

Incorrect assignment of peroxo linkage to pyrosulphuric acid.

⚠️

Student Fallacy (Why candidates pick this trap): Candidate confused peroxo (-O-O-) with oxo (-O-) bridging.

3 (3)

✓ 100% Correct

Verdict & Scientific Reason:

Accurate: Fully matches structural formulas of all four oxoacids of sulphur.

💡

Why this is airtight: None. Candidate correctly identified all bridging and terminal bonds.

4 (4)

✗ Incorrect

Verdict & Scientific Reason:

Swaps Marshall’s acid and oleum bond distributions.

⚠️

Student Fallacy (Why candidates pick this trap): Candidate inverted Marshall’s acid and oleum bridges.

⚠️

NTA Trap Alert: Mixing up Peroxodisulphuric and Pyrosulphuric Acid

Both H₂S₂O₈ and H₂S₂O₇ have two S-OH and four S=O bonds. The ONLY structural difference is the central bridge: H₂S₂O₈ has a peroxo bridge (S-O-O-S), while H₂S₂O₇ has an ether-like oxygen bridge (S-O-S).

🛡️ How to avoid the -1 mark: Mnemonic: "Peroxo has Pair of oxygens (O-O)".

📖

Core NEET Syllabus Standard

National Eligibility cum Entrance Test (NEET UG) · The p-Block Elements Standard Benchmark

Core Scientific Principle Tested:

"Oxoacids of sulphur display varied coordination with characteristic S=O, S-OH, S-O-S, and peroxo S-O-O-S linkages."

Syllabus Focus: Group 16 Elements – Oxoacids of Sulphur

Preserved in Rationalized Curriculum Syllabus & Academic Standards ↗

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NEET 2023 Chemistry Question 86 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Peroxo Bridge Scan: Marshall’s Acid (H₂S₂O₈) Uniquely Contains S–O–O–S Bridge (A → III)

Step-by-Step Rigorous Workflow & Mathematical Proof

Structure of Peroxodisulphuric Acid (H₂S₂O₈)

Structure of Sulphuric Acid (H₂SO₄)

Structure of Pyrosulphuric Acid (H₂S₂O₇)

Structure of Sulphurous Acid (H₂SO₃)

360° Option Elimination Engine Key Feature

NTA Trap Alert: Mixing up Peroxodisulphuric and Pyrosulphuric Acid

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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