Redox Reactions - NEET Previous Year Questions with Complete Solutions

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Why Redox Reactions Is a Must-Master Chapter for NEET 

Redox Reactions (Class 11, Chapter 8) is one of the most cross-functional chapters in all of NEET Chemistry. It contributes 2–3 direct questions every year — but more importantly, the skills it builds (oxidation number calculation, identifying oxidising/reducing agents, balancing equations) are used in Electrochemistry, Coordination Compounds, Inorganic Chemistry, and p-Block Elements throughout Class 12.

A student who has not mastered oxidation number rules will lose marks not just in the Redox Reactions section but across multiple chapters — making this chapter a high-leverage investment. The good news is that the question types are highly predictable: almost every Redox question in NEET tests one of five skills — oxidation number calculation, agent identification, disproportionation, balancing half-reactions, or electrochemical cell relationships.

💡 Expert Tip by eSaral Chemistry Faculty: "Oxidation number calculation is the backbone of Redox Reactions — and it is tested in NEET directly at least once every year. The rules are simple and finite. A student who has drilled the oxidation number rules for 30 minutes and then solved 20 practice problems will get every oxidation number question in NEET correct. There is almost no other topic in Chemistry where 30 minutes of focused practice guarantees full marks — take advantage of it."

NEET Previous Year Questions — Redox Reactions with Solutions 

Chapter Overview: Topics and Subtopics 

What This Chapter Covers

NEET Weightage Analysis: Year-Wise Question Count 

How Many Questions Come From Redox Reactions in NEET?

Average: 2.4 questions per year — approximately 10 marks. Given that oxidation number skills feed into multiple other chapters, the effective return from mastering this chapter is considerably higher.

💡 Expert Tip by eSaral Chemistry Faculty: "Disproportionation reactions appear in NEET almost every alternate year — and students consistently lose these marks. The rule is simple: in a disproportionation reaction, one element in the reactant is simultaneously oxidised and reduced. So the same element must appear in two different products with different oxidation states. When you see a question asking which of the following is a disproportionation reaction — check whether the same element is in multiple products with different oxidation numbers."

Key Concepts You Must Know Before Solving PYQs 

1. Oxidation Number Rules — Complete Reference

These rules must be applied in strict priority order (Rule 1 overrides Rule 2, etc.):

Critical Exceptions Tested Directly in NEET

2. Identifying Oxidising and Reducing Agents

Memory rule — OIL RIG:

• Oxidation Is Loss (of electrons)
• Reduction Is Gain (of electrons)

Step-by-step agent identification:

1. Assign oxidation numbers to all atoms in reactants and products
2. Identify which atom's oxidation number increased → that element was oxidised → its compound is the reducing agent
3. Identify which atom's oxidation number decreased → that element was reduced → its compound is the oxidising agent

3. Types of Redox Reactions

Disproportionation — Key Examples for NEET

4. Balancing Redox Reactions — Ion-Electron (Half-Reaction) Method

Steps for Acidic Medium:

1. Write separate half-reactions for oxidation and reduction
2. Balance all atoms except O and H
3. Balance O atoms by adding H₂O to the deficient side
4. Balance H atoms by adding H⁺ to the deficient side
5. Balance charges by adding electrons (e⁻) to the more positive side
6. Multiply half-reactions to equalise electrons transferred
7. Add the two balanced half-reactions; cancel common terms

Steps for Basic Medium: Steps 1–5 same as acidic, then: 6. Add equal OH⁻ to both sides to neutralise H⁺ (H⁺ + OH⁻ → H₂O) 7. Simplify

5. Quick Oxidation Number Calculation — Worked Examples

How to Study Redox Reactions for Maximum NEET Marks 

Step-by-Step Study Plan

Step 1 — Memorise the oxidation number rules in priority order (Day 1) Write all nine oxidation number rules on a single card. The priority order matters — Rule 5 (F = −1 always) overrides Rule 6 (O = −2 usually), which is why O = +2 in OF₂. Practise applying the rules to 15 compounds immediately after writing them. Target: any oxidation number calculated in under 45 seconds.

Step 2 — Build the exceptions table (Day 1) Make a dedicated flashcard for oxidation number exceptions: H₂O₂ (O = −1), OF₂ (O = +2), NaH (H = −1), KO₂ (O = −½), and unusual oxidation states of S, N, Cr, Mn, and Cl in common compounds. These exceptions account for approximately 60% of all oxidation number questions in NEET.

Step 3 — Practise oxidising/reducing agent identification with 10 reactions (Day 2) For each reaction, assign oxidation numbers to all atoms, identify which element's oxidation number increased (oxidised = reducing agent) and which decreased (reduced = oxidising agent). The OIL RIG mnemonic keeps direction clear: Oxidation Is Loss (of electrons), Reduction Is Gain.

Step 4 — Study disproportionation reactions with 4 examples (Day 2) Learn the four main disproportionation reactions: Cl₂ + NaOH, H₂O₂ decomposition, P₄ + NaOH, and HClO₃. For each, verify that the same element appears in two products with different oxidation states. This is the entire skill NEET tests for disproportionation — recognition, not derivation.

Step 5 — Practise balancing half-reactions in acidic medium (Day 3) Work through the ion-electron method for 3–4 standard half-reactions: MnO₄⁻ → Mn²⁺, Cr₂O₇²⁻ → Cr³⁺, and one involving sulphur or nitrogen. The sequence (balance atoms → add H₂O for O → add H⁺ for H → add e⁻ for charge) must be automatic.

Step 6 — Solve PYQs year-wise from 2024 to 2017 (Day 4) Work through all NEET Redox Reactions PYQs from the complete NEET chapter-wise PYQ collection on eSaral. For every question, identify which of the five concept areas it tests. After completing 5 years of PYQs, the chapter's question space will feel completely familiar.

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