Class 11 Chemistry – Redox Reactions

CBSE 2026–27 | NCERT-aligned free study resource

Oxidation and Reduction

Oxidation may be described as loss of electrons, increase in oxidation number or addition of oxygen/removal of hydrogen in suitable reactions. Reduction is the complementary process.

Oxidation Number

Oxidation number is a bookkeeping quantity used to track electron transfer. Assign oxidation numbers using standard rules and ensure that their algebraic sum matches the overall charge.

Oxidising and Reducing Agents

An oxidising agent accepts electrons and is reduced. A reducing agent donates electrons and is oxidised.

Balancing Redox Reactions

Redox equations can be balanced using oxidation-number or half-reaction approaches. Charge and atoms must be conserved.

MCQs

1. Oxidation involves: (A) gain of electrons (B) loss of electrons (C) no electron change (D) neutron loss. Answer: B.
2. An oxidising agent is itself: (A) oxidised (B) reduced (C) unchanged always (D) vaporised. Answer: B.
3. Oxidation number of oxygen is usually: (A) +2 (B) −2 (C) +1 (D) 0 in every compound. Answer: B.

Practice

1. Assign oxidation numbers in polyatomic ions.
2. Identify oxidising and reducing agents in reactions.
3. Balance redox equations and verify both atoms and charge.

HOTS

In a reaction, one element’s oxidation number rises while another’s falls. Explain why the reaction is classified as redox even if oxygen and hydrogen are absent.

Revision

Electron transfer ↔ oxidation/reduction ↔ oxidation number ↔ agents ↔ balancing.