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Redox Reactions WBJEE MCQ & Practice Questions

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Redox Reactions Revision Guide for WBJEE Chemistry

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

For WBJEE 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 WBJEE 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.

WBJEE Chemistry · Redox Reactions · Very Very Hard

1. Oxidation means:

  • A. No oxidation-number change
  • B. Gain of protons
  • C. Loss of electrons
  • D. Gain of electrons
Answer: C
Explanation: Oxidation is electron loss.

WBJEE Chemistry · Redox Reactions · Very Very Hard

2. Reduction means:

  • A. Loss of protons
  • B. Gain of electrons
  • C. Loss of electrons
  • D. Increase in oxidation number
Answer: B
Explanation: Reduction is electron gain.

WBJEE Chemistry · Redox Reactions · Very Very Hard

3. Oxidation in an electrochemical cell occurs at:

  • A. Cathode
  • B. Salt bridge
  • C. Wire
  • D. Anode
Answer: D
Explanation: Oxidation occurs at the anode.

WBJEE Chemistry · Redox Reactions · Very Very Hard

4. Reduction in an electrochemical cell occurs at:

  • A. Salt bridge
  • B. Wire
  • C. Cathode
  • D. Anode
Answer: C
Explanation: Reduction occurs at the cathode.

WBJEE Chemistry · Redox Reactions · Very Very Hard

5. Which fundamental condition must be respected in solving Redox Reactions problems?

  • A. Assume coefficients are one
  • B. Ignore limiting conditions
  • C. Conservation of atoms and charge
  • D. Ignore units
Answer: C
Explanation: Atom and charge conservation are fundamental.

WBJEE Chemistry · Redox Reactions · Very Very Hard

6. At dynamic equilibrium relevant to Redox Reactions:

  • A. Catalyst is consumed
  • B. Forward and reverse rates are equal
  • C. All molecular motion stops
  • D. Concentrations must be equal
Answer: B
Explanation: At equilibrium forward and reverse rates are equal.

WBJEE Chemistry · Redox Reactions · Very Very Hard

7. At constant T and P a spontaneous process has:

  • A. ΔG<0
  • B. ΔG>0
  • C. ΔG=0 always
  • D. ΔH=0
Answer: A
Explanation: Spontaneity requires ΔG<0.

WBJEE Chemistry · Redox Reactions · Very Very Hard

8. A catalyst in Redox Reactions generally:

  • A. Changes ΔG°
  • B. Changes ΔH
  • C. Changes K at fixed T
  • D. Lowers activation energy without changing K at fixed T
Answer: D
Explanation: Catalysts affect kinetics, not equilibrium thermodynamics.

WBJEE Chemistry · Redox Reactions · Very Very Hard

9. A Lewis acid is:

  • A. Electron-pair acceptor
  • B. Electron-pair donor
  • C. Always proton donor
  • D. Always anion
Answer: A
Explanation: Lewis acids accept electron pairs.

WBJEE Chemistry · Redox Reactions · Very Very Hard

10. A Lewis base is:

  • A. Electron-pair acceptor
  • B. Always cation
  • C. Always oxidant
  • D. Electron-pair donor
Answer: D
Explanation: Lewis bases donate electron pairs.

WBJEE Chemistry · Redox Reactions · Very Very Hard

11. Which is a state function?

  • A. Work
  • B. Path length
  • C. Enthalpy
  • D. Heat
Answer: C
Explanation: Enthalpy is a state function.

WBJEE Chemistry · Redox Reactions · Very Very Hard

12. The correct relation is:

  • A. ΔG°=RT/K
  • B. ΔG°=-RT lnK
  • C. ΔG°=RT lnK
  • D. ΔG°=-KRT
Answer: B
Explanation: ΔG°=-RTlnK.

WBJEE Chemistry · Redox Reactions · Very Very Hard

13. For a first-order process, half-life is:

  • A. 0.693/k
  • B. k/0.693
  • C. 1/(k[A]0)
  • D. [A]0/(2k)
Answer: A
Explanation: t1/2=0.693/k.

WBJEE Chemistry · Redox Reactions · Very Very Hard

14. 0.20 mol solute in 0.50 L solution has molarity:

  • A. 2.50 M
  • B. 0.70 M
  • C. 0.40 M
  • D. 0.10 M
Answer: C
Explanation: M=0.20/0.50=0.40 M.

WBJEE Chemistry · Redox Reactions · Very Very Hard

15. For a weak acid, larger Ka means:

  • A. Stronger conjugate acid
  • B. Stronger acid
  • C. Weaker acid
  • D. No ionisation
Answer: B
Explanation: Larger Ka means greater ionisation.

WBJEE Chemistry · Redox Reactions · Very Very Hard

16. At 25°C:

  • A. pH+pOH=14
  • B. pH+pOH=7
  • C. pH=pOH always
  • D. pH+pOH=1
Answer: A
Explanation: pH+pOH=pKw=14.

WBJEE Chemistry · Redox Reactions · Very Very Hard

17. Positive E°cell implies:

  • A. No spontaneous reaction
  • B. ΔG°<0
  • C. ΔG°>0
  • D. K<1 necessarily
Answer: B
Explanation: ΔG°=-nFE°.

WBJEE Chemistry · Redox Reactions · Very Very Hard

18. An electrophile is:

  • A. Always negative
  • B. Always radical
  • C. Electron-pair acceptor
  • D. Electron-pair donor
Answer: C
Explanation: Electrophiles accept electron pairs.

WBJEE Chemistry · Redox Reactions · Very Very Hard

19. Inductive effect is transmitted through:

  • A. Ionic lattice
  • B. Sigma bonds
  • C. Pi bonds only
  • D. Hydrogen bonds
Answer: B
Explanation: Inductive effect propagates through sigma bonds.

WBJEE Chemistry · Redox Reactions · Very Very Hard

20. The actual species represented by resonance forms is:

  • A. A resonance hybrid
  • B. Rapidly oscillating forms
  • C. Only least stable form
  • D. Necessarily ionic
Answer: A
Explanation: The actual structure is a resonance hybrid.

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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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