Ch 7 covers redox reactions — assignment of oxidation numbers, identifying oxidising/reducing agents, types of redox reactions, and systematic methods for balancing redox equations.
Oxidation number (ON): charge an atom would have if all bonds were ionic. Rules: element = 0; monoatomic ion = charge; H = +1 (except metal hydrides −1); O = −2 (except peroxides −1, OF₂ +2). Types: combination, decomposition, displacement, disproportionation (same element both oxidised and reduced, e.g., 2H₂O₂ → 2H₂O + O₂).
Oxidation number method: (1) assign ON to all atoms, (2) identify which change, (3) balance increase and decrease in ON, (4) balance remaining atoms. Half-reaction method: (1) separate into oxidation and reduction half-reactions, (2) balance atoms (then O with H₂O, H with H⁺, charge with e⁻), (3) equalise electrons, (4) add half-reactions. In basic medium: add OH⁻ to neutralise H⁺.
Download: https://ncert.nic.in/textbook/pdf/kech107.pdf | Part I: https://ncert.nic.in/textbook/pdf/kech1ps.zip
A disproportionation reaction is a redox reaction where the same element is simultaneously oxidised and reduced. Example: 2H₂O₂ → 2H₂O + O₂. Here oxygen in H₂O₂ (ON = −1) is both reduced to −2 (in H₂O) and oxidised to 0 (in O₂). Another example: Cl₂ + 2NaOH → NaCl + NaClO + H₂O (Cl goes from 0 to −1 and +1).
Book a Trial + Diagnostic session. Get a personalized Learning Path with clear milestones, tutor match, and a plan recommendation — all within 24 hours.
Book Trial + Diagnostic →