: 200
Oxidation state rules: free element = 0, monoatomic ion = charge, H = +1 (hydrides: -1), O = -2 (peroxides: -1, superoxides: -1/2, OF2: +2), halogens: F always -1, others usually -1. Sum of oxidation states = charge of species. Oxidation = increase in oxidation state (loss of electrons). Reduction = decrease (gain of electrons). Oxidising agent is reduced; reducing agent is oxidised. Balancing redox (ion-electron method): (1) Split into half-reactions. (2) Balance atoms: other elements first, then O with H2O, then H with H+. (3) Balance charge with e-. (4) Equalise electrons in both half-reactions. (5) Add and cancel. For basic medium: add OH- to neutralise H+ (form H2O). Disproportionation: same element is both oxidised and reduced. Comproportionation: same element from two oxidation states combines to form intermediate state. n-factor for redox: total change in oxidation state per formula unit.