Chemistry · Ch 10 — Redox Reactions
Summary
Summary
- Classical definition: oxidation = addition of oxygen / removal of hydrogen; reduction = the reverse. Both always occur together in the same reaction.
- Electronic (modern) definition: oxidation = loss of electrons; reduction = gain of electrons. This is fully general and applies even when no oxygen or hydrogen is involved.
- Oxidizing agent = the species reduced (it causes oxidation of the other reactant); reducing agent = the species oxidized (it causes reduction of the other reactant).
- Oxidation number is the formal charge an atom would carry if every bond were treated as fully ionic, assigned by a fixed set of rules; a redox reaction is one in which at least one element's oxidation number changes.
- Types of redox reactions: combination, decomposition, displacement, and disproportionation (a single element in one oxidation state is simultaneously oxidized and reduced, e.g. ).
- Oxidation-number method: equalize total oxidation-number increase and decrease directly, then balance remaining atoms with /.
- Ion-electron (half-reaction) method: balance oxidation and reduction as two separate half-reactions (atoms, then O with , then H with , then charge with ), equalize electrons, then add; for basic medium, add to both sides afterward to remove .
- Equivalent weight = molar mass n-factor (electrons transferred per formula unit); normality ; at equivalence, . …