# Redox Reactions Notes, Class 11 Chemistry | SwaVid Redox Reactions, NCERT Class 11 Chemistry: notes with key ideas, formulas, common mistakes and 3 quick checks with worked answers. Canonical: https://www.swavid.com/cbse/class-11/chemistry/chapter/redox-reactions Source: https://www.swavid.com/cbse/class-11/chemistry/chapter/redox-reactions # Redox Reactions ## Formulas and definitions ## Key ideas ## Common mistakes ## Quick checks ## Keep going ## Questions parents ask ## Class 11 Chemistry on SwaVid ### Classical and electron transfer concepts ### Oxidation number concept ### Types of redox reactions ### Balancing redox reactions ### Redox reactions and electrode processes ### Next chapter ### Related chapter ### Related chapter ### All chapters SwaVid › CBSE › Class 11 › Chemistry › Redox Reactions Notes written by SwaVid from the NCERT textbook. Class 11 Chemistry, Unit 7. Key ideas, formulas and common mistakes. CBSE prints 4 marks for Unit 7, not for this chapter alone. Short answer. This chapter explains oxidation-reduction reactions using classical, electron transfer, and oxidation number methods. Students learn to determine oxidation states, balance redox reactions, and understand the working of electrochemical cells. Source: NCERT Chemistry Part II (Reprint 2026-27) , Unit 7, Redox Reactions Oxidation is the addition of oxygen or an electronegative element, or the removal of hydrogen or an electropositive element. Reduction is the addition of hydrogen or an electropositive element, or the removal of oxygen or an electronegative element. In electron transfer terms, oxidation is the loss of electrons and reduction is the gain of electrons. Oxidation number denotes the oxidation state of an element in a compound calculated according to a set of rules where electron pairs in a covalent bond belong to the more electronegative element. An increase in oxidation number represents oxidation, while a decrease represents reduction. Redox reactions are classified into combination, decomposition, displacement, and disproportionation reactions. In a disproportionation reaction, an element in one oxidation state is simultaneously oxidized and reduced. Redox reactions are balanced using either the oxidation number method or the half-reaction method. Both methods ensure that the total change in oxidation number or the total number of electrons lost equals the electrons gained, followed by balancing atoms and charges. An electrochemical cell converts chemical energy released in a redox reaction into electrical energy. Oxidation takes place at the anode, reduction occurs at the cathode, and electrons flow from anode to cathode through an external circuit. Try each question first. Then tap it to see the answer. Let the oxidation state of Cr be x. The oxidation state of oxygen is usually -2. Sum of oxidation states: 2x + 7(-2) = -2 2x - 14 = -2 2x = +12 x = +6 +6 Let the oxidation state of P be x. Assign +1 for H and -2 for O. 2(+1) + x + 4(-2) = -1 2 + x - 8 = -1 x - 6 = -1 x = +5 +5 Oxidation state of O in H₂O₂ is -1. Oxidation state of O in H₂O is -2. Oxidation state of O in O₂ is 0. Oxygen changes from -1 to -2 (reduction) and from -1 to 0 (oxidation). Oxygen Organic Chemistry - Some Basic Principles and Techniques . Chemical Bonding and Molecular Structure . Equilibrium . The 9 chapters of Class 11 Chemistry . CBSE does not give marks to one chapter. It prints 4 marks for Unit 7, Redox Reactions, which includes Redox Reactions. No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed. Organic Chemistry - Some Basic Principles and Techniques. SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works. - Unit 7 NCERT book - 4 marks, Unit 7 - 3 quick checks - Assigning a -2 oxidation state to oxygen in peroxides and superoxides . Check the chemical structure and identify peroxide bonds (O-O) where oxygen has an oxidation state of -1, or superoxides where it is -1/2. - Assuming hydrogen always has an oxidation number of +1 . Look for binary compounds with electropositive active metals like NaH or CaH₂, where hydrogen forms a hydride ion with an oxidation state of -1. - Balancing charges with H⁺ in an alkaline medium . In basic solutions, balance charges by adding OH⁻ ions to the side deficient in negative charge, or add equal OH⁻ to both sides after balancing with H⁺. - Confusing oxidizing agents with the substance oxidized . Remember that the substance undergoing oxidation acts as the reducing agent, and the substance undergoing reduction acts as the oxidizing agent. ## Key Links - [CBSE](https://www.swavid.com/cbse) - [Class 11](https://www.swavid.com/cbse/class-11) - [Chemistry](https://www.swavid.com/cbse/class-11/chemistry/chapters) - [Start free →](https://www.swavid.com/signup) - [All 9 chapters](https://www.swavid.com/cbse/class-11/chemistry/chapters) - [NCERT Chemistry Part II (Reprint 2026-27)](https://ncert.nic.in/textbook.php) - [Open notes](https://www.swavid.com/cbse/class-11/chemistry/chapter/organic-chemistry-some-basic-principles-and-techniques) - [Open notes](https://www.swavid.com/cbse/class-11/chemistry/chapter/chemical-bonding-and-molecular-structure) - [Open notes](https://www.swavid.com/cbse/class-11/chemistry/chapter/equilibrium) - [Class 11 Chemistry](https://www.swavid.com/cbse/class-11/chemistry/chapters) - [Start free →](https://www.swavid.com/signup)