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Redox Reactions ISC Class 11 MCQ & Practice Questions

Practice Redox Reactions MCQs for ISC Class 11 Chemistry with answers, explanations, chapter revision and related ChemNexa mock tests.

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Redox Reactions Revision Guide for ISC Class 11 Chemistry

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

For ISC Class 11 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 ISC Class 11 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.

ISC Class 11 Chemistry · Redox Reactions · Very Hard

1. A decrease in oxidation number signifies:

  • A. Oxidation
  • B. Hydrolysis
  • C. No redox change
  • D. Reduction
Answer: D
Explanation: Reduction corresponds to a decrease in oxidation state.

ISC Class 11 Chemistry · Redox Reactions · Very Hard

2. An increase in oxidation number signifies:

  • A. Oxidation
  • B. Reduction
  • C. Neutralisation
  • D. Precipitation
Answer: A
Explanation: Oxidation corresponds to an increase in oxidation state.

ISC Class 11 Chemistry · Redox Reactions · Very Hard

3. Oxidation in terms of electrons means:

  • A. Gain of protons
  • B. Loss of neutrons
  • C. Loss of electrons
  • D. Gain of electrons
Answer: C
Explanation: Oxidation is electron loss.

ISC Class 11 Chemistry · Redox Reactions · Very Hard

4. Reduction in terms of electrons means:

  • A. Loss of hydrogen
  • B. Gain of electrons
  • C. Loss of electrons
  • D. Gain of oxygen
Answer: B
Explanation: Reduction is electron gain.

ISC Class 11 Chemistry · Redox Reactions · Very Hard

5. Oxidation can also be described as:

  • A. Addition of oxygen
  • B. Removal of oxygen
  • C. Addition of electrons
  • D. Decrease in oxidation number
Answer: A
Explanation: Classically, oxidation includes addition of oxygen.

ISC Class 11 Chemistry · Redox Reactions · Very Hard

6. Reduction can also be described as:

  • A. Addition of oxygen
  • B. Loss of electrons
  • C. Increase in oxidation number
  • D. Removal of oxygen
Answer: D
Explanation: Classically, reduction includes removal of oxygen.

ISC Class 11 Chemistry · Redox Reactions · Very Hard

7. The oxidation number of an element in its free state is:

  • A. -1
  • B. Equal to atomic number
  • C. 0
  • D. +1
Answer: C
Explanation: Atoms in an uncombined elemental substance have oxidation number zero.

ISC Class 11 Chemistry · Redox Reactions · Very Hard

8. The oxidation number of a monatomic ion equals:

  • A. Its mass number
  • B. Its ionic charge
  • C. Always zero
  • D. Its atomic number
Answer: B
Explanation: For a monatomic ion, oxidation number equals the net charge.

ISC Class 11 Chemistry · Redox Reactions · Very Hard

9. The usual oxidation number of oxygen in compounds is:

  • A. -2
  • B. +2
  • C. -1
  • D. 0
Answer: A
Explanation: Oxygen is usually assigned -2 except in peroxides, superoxides and compounds with fluorine.

ISC Class 11 Chemistry · Redox Reactions · Very Hard

10. The oxidation number of oxygen in H2O2 is:

  • A. -2
  • B. 0
  • C. +1
  • D. -1
Answer: D
Explanation: Hydrogen peroxide is a peroxide, where each oxygen has oxidation number -1.

ISC Class 11 Chemistry · Redox Reactions · Very Hard

11. The oxidation number of oxygen in OF2 is:

  • A. -1
  • B. +1
  • C. +2
  • D. -2
Answer: C
Explanation: Fluorine is always -1 in compounds, forcing oxygen to +2 in OF2.

ISC Class 11 Chemistry · Redox Reactions · Very Hard

12. The usual oxidation number of hydrogen with non-metals is:

  • A. +2
  • B. +1
  • C. -1
  • D. 0
Answer: B
Explanation: Hydrogen is generally +1 when bonded to non-metals.

ISC Class 11 Chemistry · Redox Reactions · Very Hard

13. The oxidation number of hydrogen in NaH is:

  • A. -1
  • B. +1
  • C. 0
  • D. +2
Answer: A
Explanation: In metal hydrides hydrogen has oxidation number -1.

ISC Class 11 Chemistry · Redox Reactions · Very Hard

14. Fluorine in its compounds has oxidation number:

  • A. +1
  • B. 0
  • C. Variable from -1 to +7
  • D. -1
Answer: D
Explanation: Fluorine is the most electronegative element and is assigned -1 in compounds.

ISC Class 11 Chemistry · Redox Reactions · Very Hard

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

  • A. -1
  • B. Equal to molar mass
  • C. 0
  • D. 1
Answer: C
Explanation: Oxidation numbers sum to the overall charge, which is zero for a neutral species.

ISC Class 11 Chemistry · Redox Reactions · Very Hard

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

  • A. Atomic number of central atom
  • B. The ionic charge
  • C. Always zero
  • D. Number of atoms
Answer: B
Explanation: The algebraic sum equals the ion's net charge.

ISC Class 11 Chemistry · Redox Reactions · Very Hard

17. The oxidation number of sulfur in H2SO4 is:

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

ISC Class 11 Chemistry · Redox Reactions · Very Hard

18. The oxidation number of nitrogen in HNO3 is:

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

ISC Class 11 Chemistry · Redox Reactions · Very Hard

19. The oxidation number of Mn in KMnO4 is:

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

ISC Class 11 Chemistry · Redox Reactions · Very Hard

20. The oxidation number of Cr in K2Cr2O7 is:

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

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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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