Zn²⁺
Cu²⁺
Electrochemistry
World B — Acids, Bases & Solutions
21.A — REDOX FUNDAMENTALS
M
R21.01 Oxidation
- Loss of electrons.
- Increase in oxidation state.
- Addition of Oxygen / Removal of Hydrogen.
N
R21.02 Reduction
- Gain of electrons.
- Decrease in oxidation state.
- Addition of Hydrogen / Removal of Oxygen.
A
B
R21.03 Redox Reactions
- Oxidation and Reduction occur simultaneously.
- Electrons transferred from one species to another.
- Total charge and mass are conserved.
R21.04 Oxidation States
- Formal charge atom would have if ionic.
- Free elements = 0.
- Sum of states in neutral molecule = 0.
OA
Gets ReducedRA
Gets Oxidized
R21.05 Oxidizing & Reducing Agents
- Oxidizing Agent: Accepts electrons (is reduced).
- Reducing Agent: Donates electrons (is oxidized).
Fe → Fe²⁺+ 2e⁻
2e⁻ +Cu²⁺ → Cu
R21.06 Half-Reactions
- Splitting redox into two separate equations.
- Helps balance complex reactions (Ion-electron method).
- Electrons must cancel out when combined.
21.B — ELECTRODES & CONDUCTION
R21.07 Electrodes
- Anode: Where Oxidation occurs.
- Cathode: Where Reduction occurs.
- Conductive surfaces for electron transfer.
+
-
R21.08 Electrolytes
- Substances that dissociate into ions in solution/melt.
- Internal circuit medium.
- Allows ion migration to maintain charge balance.
💡
R21.09 Conductance in Solutions
- Ability of ions to move and carry charge.
- Increases with dilution for weak electrolytes (Kohlrausch's Law).
- Depends on ion concentration and mobility.
21.C — THERMODYNAMICS & POTENTIALS
R21.10 Electrochemical Series
- Elements ranked by Standard Reduction Potential (E°).
- Top: Strongest reducing agents (Li, K).
- Bottom: Strongest oxidizing agents (F₂, Au).
R21.11 Standard Hydrogen Electrode
- The universal reference electrode (SHE).
- Assigned a potential of exactly 0.00 V.
- Pt wire in 1M H⁺ solution with H₂ gas at 1 atm.
E = E° - (RT/nF)lnQ
R21.12 Nernst Equation
- Relates cell potential to concentration/temp.
- Voltage drops as reactants are consumed.
- When battery is dead, E = 0 and Q = K.