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)

⚡

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!

🛡️

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

📐

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).

⭐

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.

⚠️

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!

📖

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!

Ready to attempt under real exam pressure?

Test your speed and accuracy in the authentic 180-minute timed NTA simulator.

Launch NEET 2025 CBT Test →

← Previous (Q.54) All Chemistry Questions Grid Next (Q.56) →

Spotted a mistake in this solution? Report an error ([email protected])

⚖️ Legal & Fair Dealing Notice: Sourced from publicly released NEET 2025 question papers and NEET answer keys for private study, research, and non-commercial educational practice under Fair Dealing (Section 52(1)(a) of the Indian Copyright Act, 1957). Not affiliated with or endorsed by NTA or NMC.

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

Solve 4 NEET Questions a Day — One per Subject