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Redox Reactions JEE Main MCQ & Practice Questions

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Redox Reactions Revision Guide for JEE Main Chemistry

Redox Reactions focuses on electron transfer and oxidation-state changes. It supports electrochemistry, inorganic reactions and many analytical calculations.

For JEE Main Chemistry, practise oxidation-number rules, identifying oxidising and reducing agents, balancing redox equations and equivalent concepts where they are part of the syllabus.

Important Topics

  • Oxidation number rules
  • Oxidation and reduction
  • Oxidising and reducing agents
  • Balancing by oxidation-number method
  • Ion-electron method
  • Redox stoichiometry

Important Formulae & Relationships

  • Increase in oxidation number = oxidation
  • Decrease in oxidation number = reduction
  • Total electrons lost = total electrons gained in a balanced redox process

Use formulas only after checking the required units, sign convention and assumptions for the question.

What to practise in Redox Reactions

Concept Revision

Revise definitions, principles, equations, trends and core ideas from Redox Reactions before attempting MCQs.

Exam-style MCQs

Use chapter-focused multiple-choice practice to improve accuracy, recall and application for JEE Main Chemistry.

Performance Practice

Attempt ChemNexa tests, review results and return to weak areas for another round of targeted revision.

Top 20 Redox Reactions MCQs with Answers

These public questions are selected from the exact Redox Reactions chapter, screened for topic relevance and deduplicated so repeated versions of the same MCQ are not shown publicly. Use them for quick revision, then sign in to attempt the complete test experience with more questions, results and performance review.

JEE Main Chemistry · Redox Reactions · Very Hard

1. Reduction is best defined as:

  • A. Loss of hydrogen only
  • B. Gain of electrons or decrease in oxidation number
  • C. Loss of electrons only
  • D. Increase in oxidation number
Answer: B
Explanation: Reduction involves electron gain and a decrease in oxidation number.

JEE Main Chemistry · Redox Reactions · Very Hard

2. Oxidation is best defined as:

  • A. Decrease in oxidation number
  • B. Gain of hydrogen only
  • C. Loss of electrons or increase in oxidation number
  • D. Gain of electrons only
Answer: C
Explanation: Oxidation involves electron loss and an increase in oxidation number.

JEE Main Chemistry · Redox Reactions · Very Hard

3. An oxidising agent:

  • A. Accepts electrons and is reduced
  • B. Donates electrons and is oxidised
  • C. Never changes oxidation state
  • D. Always contains oxygen
Answer: A
Explanation: An oxidising agent causes oxidation by accepting electrons and itself undergoing reduction.

JEE Main Chemistry · Redox Reactions · Very Hard

4. A reducing agent:

  • A. Accepts electrons and is reduced
  • B. Always contains hydrogen
  • C. Never changes oxidation state
  • D. Donates electrons and is oxidised
Answer: D
Explanation: A reducing agent supplies electrons and itself undergoes oxidation.

JEE Main Chemistry · Redox Reactions · Very Hard

5. The oxidation number of oxygen in most compounds is:

  • A. +2
  • B. 0
  • C. -2
  • D. -1
Answer: C
Explanation: Oxygen normally has oxidation number -2, except in peroxides, superoxides and compounds with fluorine.

JEE Main Chemistry · Redox Reactions · Very Hard

6. The oxidation number of oxygen in H2O2 is:

  • A. +1
  • B. -1
  • C. -2
  • D. 0
Answer: B
Explanation: Peroxide oxygen has oxidation number -1.

JEE Main Chemistry · Redox Reactions · Very Hard

7. The oxidation number of oxygen in KO2 is:

  • A. -1/2
  • B. -1
  • C. -2
  • D. +1/2
Answer: A
Explanation: In superoxide O2-, each oxygen has an average oxidation number of -1/2.

JEE Main Chemistry · Redox Reactions · Very Hard

8. The oxidation number of oxygen in OF2 is:

  • A. -2
  • B. -1
  • C. 0
  • D. +2
Answer: D
Explanation: Fluorine is -1, so oxygen must be +2 in OF2.

JEE Main Chemistry · Redox Reactions · Very Hard

9. The oxidation number of hydrogen in metal hydrides is:

  • A. 0
  • B. +2
  • C. -1
  • D. +1
Answer: C
Explanation: In ionic metal hydrides such as NaH, hydrogen is -1.

JEE Main Chemistry · Redox Reactions · Very Hard

10. The oxidation number of Mn in KMnO4 is:

  • A. +2
  • B. +7
  • C. +6
  • D. +4
Answer: B
Explanation: K is +1 and four oxygens contribute -8, so Mn is +7.

JEE Main Chemistry · Redox Reactions · Very Hard

11. The oxidation number of Cr in K2Cr2O7 is:

  • A. +6
  • B. +3
  • C. +7
  • D. +4
Answer: A
Explanation: 2(+1)+2x+7(-2)=0 gives x=+6.

JEE Main Chemistry · Redox Reactions · Very Hard

12. The oxidation number of S in H2SO4 is:

  • A. +4
  • B. +2
  • C. -2
  • D. +6
Answer: D
Explanation: 2(+1)+x+4(-2)=0 gives x=+6.

JEE Main Chemistry · Redox Reactions · Very Hard

13. The oxidation number of N in NH3 is:

  • A. -1
  • B. +5
  • C. -3
  • D. +3
Answer: C
Explanation: x+3(+1)=0 gives x=-3.

JEE Main Chemistry · Redox Reactions · Very Hard

14. The oxidation number of N in HNO3 is:

  • A. +1
  • B. +5
  • C. +3
  • D. -3
Answer: B
Explanation: (+1)+x+3(-2)=0 gives x=+5.

JEE Main Chemistry · Redox Reactions · Very Hard

15. In disproportionation, the same species is:

  • A. Simultaneously oxidised and reduced
  • B. Only oxidised
  • C. Only reduced
  • D. Neither oxidised nor reduced
Answer: A
Explanation: A single oxidation state changes to both a higher and a lower oxidation state.

JEE Main Chemistry · Redox Reactions · Very Hard

16. In comproportionation, two oxidation states combine to form:

  • A. Only the lowest oxidation state
  • B. No redox product
  • C. An intermediate oxidation state
  • D. Only the highest oxidation state
Answer: C
Explanation: Comproportionation is the reverse of disproportionation.

JEE Main Chemistry · Redox Reactions · Very Hard

17. The sum of oxidation numbers in a neutral molecule is:

  • A. Equal to the number of atoms
  • B. Zero
  • C. +1
  • D. -1
Answer: B
Explanation: A neutral species has zero total charge.

JEE Main Chemistry · Redox Reactions · Very Hard

18. The sum of oxidation numbers in a polyatomic ion equals:

  • A. The ionic charge
  • B. Zero always
  • C. The number of atoms
  • D. The oxidation number of oxygen
Answer: A
Explanation: The algebraic sum equals the net charge on the ion.

JEE Main Chemistry · Redox Reactions · Very Hard

19. In the ion-electron method, atoms other than H and O are balanced:

  • A. Using electrons first
  • B. Before balancing H and O
  • C. After balancing charge only
  • D. Never
Answer: B
Explanation: The usual sequence balances the central redox atoms before O, H and charge.

JEE Main Chemistry · Redox Reactions · Very Hard

20. In the reaction Zn + Cu2+ -> Zn2+ + Cu, zinc is:

  • A. Reduced
  • B. Neither
  • C. A catalyst
  • D. Oxidised
Answer: D
Explanation: Zn changes from 0 to +2 and loses electrons.

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Redox Reactions Practice Tests

Redox Reactions Frequently Asked Questions

How do I identify the oxidising agent?

The oxidising agent causes another species to be oxidised and is itself reduced.

What is the safest way to balance redox equations?

Use either the oxidation-number method or ion-electron method systematically, then verify both atom balance and total charge.

Why is oxidation state useful?

It provides a bookkeeping method for identifying electron-transfer changes even when electrons do not appear explicitly in the written equation.

Continue with another chapter to build connected concepts and strengthen your overall Chemistry preparation.

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