Class 11 Chemistry Chapter 7 Redox Reactions – Revision Notes

Redox reactions pair oxidation, where an atom loses electrons and its oxidation number rises, with reduction, where electrons are gained and the oxidation number falls. This chapter sets out the rules for assigning oxidation numbers, distinguishes oxidizing from reducing agents, and covers disproportionation along with two methods for balancing redox equations.

Last Updated: September 23, 2026

Oxidation and Reduction

• Oxidation: loss of electrons (oxidation number increases).
• Reduction: gain of electrons (oxidation number decreases).

Oxidation Number Rules

• Free element=0; O usually −2; H usually +1.

Agents and Types

• Oxidizing agent: gets reduced. Reducing agent: gets oxidized.
• Disproportionation: same element oxidized and reduced.

Balancing Methods

• Oxidation number method; ion-electron (half-reaction) method.

One-Line Summary

Redox reactions involve simultaneous oxidation (electron loss) and reduction (electron gain), tracked using oxidation numbers and balanced via the oxidation number or half-reaction methods.

Frequently Asked Questions

What is the difference between oxidation and reduction in terms of electron transfer?
Oxidation involves the loss of electrons by a substance, increasing its oxidation number, while reduction involves the gain of electrons, decreasing its oxidation number, and the two always occur together in a redox reaction.

What is the role of oxidation numbers in balancing redox equations?
Assigning oxidation numbers to each atom helps track how many electrons are lost or gained during the reaction, allowing the oxidation and reduction half-reactions to be balanced so electrons lost equal electrons gained overall.

Written by Satish

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