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Redox Reactions WBCHSE Class 11 MCQ & Practice Questions

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

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Redox Reactions Revision Guide for WBCHSE Class 11 Chemistry

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

For WBCHSE 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 WBCHSE 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

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WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

1. Reduction in an oxidation-number description means:

  • A. Increase in oxidation number
  • B. No change
  • C. Always formation of an anion
  • D. Decrease in oxidation number
Answer: D
Explanation: Reduction corresponds to a decrease in oxidation state.

WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

2. The usual oxidation number of oxygen in most compounds is:

  • A. -2
  • B. -1
  • C. +2
  • D. 0
Answer: A
Explanation: Oxygen usually has oxidation state -2.

WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

3. The oxidation number of oxygen in peroxides is:

  • A. -2
  • B. 0
  • C. +1
  • D. -1
Answer: D
Explanation: Each oxygen atom in a peroxide has oxidation state -1.

WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

4. Oxidation in an oxidation-number description means:

  • A. Increase in oxidation number
  • B. Decrease in oxidation number
  • C. No change in oxidation number
  • D. Oxidation number becomes zero only
Answer: A
Explanation: Oxidation corresponds to an increase in oxidation state.

WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

5. Oxidation is best defined in terms of electrons as:

  • A. Sharing of electrons only
  • B. No change in electrons
  • C. Loss of electrons
  • D. Gain of electrons
Answer: C
Explanation: Oxidation corresponds to loss of electrons.

WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

6. Reduction is best defined in terms of electrons as:

  • A. Increase of oxygen always
  • B. Gain of electrons
  • C. Loss of electrons
  • D. Loss of protons only
Answer: B
Explanation: Reduction corresponds to gain of electrons.

WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

7. An oxidising agent itself undergoes:

  • A. Reduction
  • B. Oxidation
  • C. No change
  • D. Neutralisation only
Answer: A
Explanation: An oxidising agent accepts electrons and is reduced.

WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

8. Addition of oxygen to a substance is conventionally regarded as:

  • A. Neutralisation
  • B. Hydrolysis
  • C. Oxidation
  • D. Reduction
Answer: C
Explanation: Classically, gain of oxygen is oxidation.

WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

9. Removal of oxygen from a compound is conventionally regarded as:

  • A. Precipitation
  • B. Reduction
  • C. Oxidation
  • D. Disproportionation
Answer: B
Explanation: Classically, loss of oxygen is reduction.

WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

10. Addition of hydrogen to a substance is generally regarded as:

  • A. Reduction
  • B. Oxidation
  • C. Combustion
  • D. Ionisation
Answer: A
Explanation: Gain of hydrogen is a classical definition of reduction.

WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

11. Removal of hydrogen from a substance is generally regarded as:

  • A. Reduction
  • B. Hydration
  • C. Neutralisation
  • D. Oxidation
Answer: D
Explanation: Loss of hydrogen is a classical definition of oxidation.

WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

12. 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: Uncombined elements have oxidation number zero.

WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

13. The oxidation number of a monatomic ion equals its:

  • A. Number of neutrons
  • B. Ionic charge
  • C. Mass number
  • D. Atomic number
Answer: B
Explanation: For a monatomic ion, oxidation number equals the net charge.

WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

14. The oxidation number of oxygen in OF2 is:

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

WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

15. Hydrogen usually has oxidation number:

  • A. +2
  • B. +1
  • C. -1
  • D. 0
Answer: B
Explanation: Hydrogen is usually +1 when bonded to nonmetals.

WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

16. In metal hydrides such as NaH, hydrogen has oxidation number:

  • A. -1
  • B. +1
  • C. 0
  • D. -2
Answer: A
Explanation: Hydrogen is -1 in ionic metal hydrides.

WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

17. 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 -1 in compounds.

WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

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

  • A. -1
  • B. Equal to number of atoms
  • C. 0
  • D. +1
Answer: C
Explanation: Oxidation numbers sum to the overall charge, zero for a neutral molecule.

WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

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

  • A. Number of atoms
  • B. The ionic charge
  • C. Zero always
  • D. Atomic number of central atom
Answer: B
Explanation: The sum equals the net charge on the ion.

WBCHSE Class 11 Chemistry · Redox Reactions · Very Hard

20. 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, giving S=+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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