Q.55 Chemistry ⭐ 360° Option Elimination Active

NEET 2025 Chemistry Question 55 Solution

Topic: Redox Reactions · Official NTA Booklet Code 45

Question

Consider the following compounds: K̲O₂, H₂O̲₂ and H₂S̲O₄. The oxidation states of the underlined elements in them are, respectively,

✓

Verified Against NTA Final Answer Key

Option (1) : +1, -1, and +6

📚 Redox Reactions Easy

📋 Given Parameters & Problem Setup

Species 1 KO₂ (Potassium superoxide)

Species 2 H₂O₂ (Hydrogen peroxide)

Species 3 H₂SO₄ (Sulfuric acid)

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The 30-Second Exam Hall Shortcut: ⚡ Alkali Metal and Peroxide Invariance

⏱️ Save ~25 seconds

K is Group 1 alkali metal: ALWAYS +1 in all compounds! In peroxide (H₂O₂), O is ALWAYS -1! In H₂SO₄: 2(+1) + S + 4(-2) = 0 ⟹ S = +6! Answer: +1, -1, +6!

1 Look at Potassium in KO₂: Potassium is an alkali metal and exhibits ONLY a +1 oxidation state in its chemical compounds. (The superoxide ion is O₂⁻, where each oxygen has oxidation state -1/2).

2 Look at Oxygen in H₂O₂: Hydrogen peroxide contains a peroxide linkage (-O-O-). Each hydrogen is +1, so 2(+1) + 2(O) = 0 ⟹ O = -1.

3 Look at Sulfur in H₂SO₄: 2(+1) + S + 4(-2) = 0 ⟹ 2 + S - 8 = 0 ⟹ S = +6.

4 Sequential oxidation states: +1, -1, +6.

5 Match Option (1) in under 10 seconds!

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Why You Can 100% Trust This Shortcut: Rules for Assigning Oxidation Numbers (NCERT Chemistry · Redox Reactions).

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Oxidation State of K in KO₂

Potassium (K) is an alkali metal (Group 1). By the canonical rules for oxidation numbers, alkali metals strictly exhibit an oxidation state of +1 in all their compounds:

\text{In } \underline{\text{K}}\text{O}_2: \quad \text{O.S. of K} = +1

• The compound is potassium superoxide, consisting of K⁺ and O₂⁻ ions.
• The average oxidation state of each oxygen is -1/2.

Step 2

Oxidation State of O in H₂O₂

In hydrogen peroxide, hydrogen has an oxidation number of +1. Using the charge neutrality rule:

2(+1) + 2(x) = 0 \implies 2 + 2x = 0 \implies x = -1

• In peroxides containing the (-O-O-) single bond, oxygen has an oxidation number of -1.

Step 3

Oxidation State of S in H₂SO₄

In sulfuric acid, hydrogen is +1 and oxygen is -2:

2(+1) + x + 4(-2) = 0 \implies 2 + x - 8 = 0 \implies x = +6

• Sulfur achieves its maximum group oxidation state of +6.
• Consolidated result: +1, -1, and +6, matching Option (1).

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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

✓ 100% Correct

Verdict & Scientific Reason:

100% correct. K is +1 (alkali metal), O in peroxide is -1, and S in sulfate is +6.

💡

Why this is airtight: None; textbook oxidation state rules.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Assigns +2 to potassium (alkali metals can never have +2) and -2 to peroxide oxygen.

⚠️

Student Fallacy (Why candidates pick this trap): Treating K as alkaline earth metal and peroxide as normal oxide.

3 C

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Treats peroxide oxygen as -2 and calculates sulfur as +4.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing sulfuric acid with sulfurous acid.

4 D

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Absurd oxidation numbers for K and O.

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Student Fallacy (Why candidates pick this trap): Multiplying subscripts into oxidation numbers.

⚠️

NTA Trap Alert: The Superoxide/Peroxide Oxygen Trap

Students frequently assume oxygen is ALWAYS -2, which would erroneously make K in KO₂ equal to +4. Remembering that K is an alkali metal (fixed at +1) immediately resolves the compound as a superoxide!

🛡️ How to avoid the -1 mark: Group 1 alkali metals are ANCHORS: always assign K = +1 first!

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Core NEET Syllabus Standard

NEET Chemistry Core Syllabus · Redox Reactions Standard Benchmark

Core Scientific Principle Tested:

"Group 1 metals are +1; peroxides have O = -1; oxoacids follow neutral sum Σ O.S. = 0."

Syllabus Focus: Rules for Calculating Oxidation Numbers

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

K is always +1, Peroxide O is -1, Sulfate S is +6 ⟹ +1, -1, +6!

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NEET 2025 Chemistry Question 55 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Alkali Metal and Peroxide Invariance

Step-by-Step Rigorous Workflow & Mathematical Proof

Oxidation State of K in KO₂

Oxidation State of O in H₂O₂

Oxidation State of S in H₂SO₄

360° Option Elimination Engine Key Feature

NTA Trap Alert: The Superoxide/Peroxide Oxygen Trap

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

🔗 Related Questions — Redox Reactions

Equivalence Point & n-factor in Permanganate-Oxalate Titration

Decreasing Order of Oxidation State of Central Atoms

Identification of Non-Redox (Double Displacement) Reactions

Balancing Redox Reactions by Ion-Electron Method in Acidic Medium

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