Redox Reactions – NEET Chemistry Class 11

Redox reactions are chemical reactions that involve the transfer of electrons between species. Understanding these reactions is fundamental in chemistry as they explain processes ranging from combustion and corrosion to metabolism and industrial reactions. This chapter is frequently tested in NEET exams due to its application-based and numerical nature.

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Introduction to Redox Reactions

A redox reaction involves two simultaneous processes:

1. Oxidation – Loss of electrons by a species.

2. Reduction – Gain of electrons by a species.

The substance that gets oxidized is the reducing agent, and the substance that gets reduced is the oxidizing agent.

Oxidation Number Concept

The oxidation number (ON) is a useful tool to track electron transfer in redox reactions. Key rules include:

• The oxidation number of an element in its free state is 0.

• For a monatomic ion, ON = charge of the ion.

• In compounds, hydrogen usually has +1 and oxygen usually has -2.

• The sum of oxidation numbers in a neutral compound = 0; in ions = ion charge.

Identifying Redox Reactions

To identify a redox reaction:

• Determine the oxidation number of each atom before and after the reaction.

• An increase in ON = oxidation; a decrease in ON = reduction.

• Example: Zn + Cu²⁺ → Zn²⁺ + Cu

  • Zn: 0 → +2 (oxidation)

  • Cu: +2 → 0 (reduction)

Types of Redox Reactions

1. Combination Reactions – Two substances combine and electrons are transferred.

2. Decomposition Reactions – A compound breaks down, electron transfer may occur.

3. Displacement Reactions – A more reactive element displaces a less reactive one from a compound.

4. Disproportionation Reactions – A single species undergoes simultaneous oxidation and reduction.

Electrochemical Cells

Redox reactions are the basis of electrochemical cells, where chemical energy is converted to electrical energy. Key concepts include:

• Galvanic Cells – Spontaneous redox reactions generate electricity.

• Electrolytic Cells – Electricity drives non-spontaneous redox reactions.

• Standard Electrode Potential (E°) – Measures the tendency of a species to be reduced.

Balancing Redox Reactions

Redox reactions can be balanced using two main methods:

1. Oxidation Number Method – Adjust oxidation numbers to balance electron transfer.

2. Half-Reaction Method – Separate oxidation and reduction half-reactions, balance them, and combine.

Balancing is essential for NEET numerical questions.

Importance for NEET Preparation

Redox reactions are vital for NEET because:

• Questions can be conceptual (identifying oxidizing/reducing agents) or numerical (balancing reactions).

• Applications in electrochemistry and industrial processes are frequently tested.

• Understanding redox lays the foundation for advanced topics like electrolysis and batteries.

Previous Year NEET Questions – Insights

Common questions include:

• Identifying oxidizing and reducing agents in reactions.

• Calculating oxidation numbers and identifying oxidation/reduction processes.

• Balancing complex redox reactions using half-reaction or oxidation number methods.

• Understanding galvanic and electrolytic cell reactions.

Study Tips for Students

1. Memorize Rules for Oxidation Numbers – Essential for solving numerical problems.

2. Practice Balancing Redox Reactions – Both half-reaction and oxidation number methods.

3. Understand Electrochemical Cells – Focus on standard electrode potential and applications.

4. Solve Previous Year NEET Questions – Helps in time management and accuracy.

5. Focus on Conceptual Clarity – Identifying oxidizing/reducing agents and reaction type.

Conclusion

Mastering Redox Reactions is essential for NEET success. It enables students to understand electron transfer, solve numerical problems confidently, and tackle both theory and application-based questions. Redox concepts also form the basis for electrochemistry, industrial chemistry, and biological processes.