โก Electrochemistry
Redox reactions, electrochemical cells, electrode potentials, and electrolysis - the branch of chemistry that powers batteries, industrial processes, and metal extraction.
Oxidation is electron loss (OIL), reduction is electron gain (RIG). Oxidation states track electrons - the algebraic bookkeeping of redox chemistry.
Mn goes from +7 to +2 (reduced, gains 5eโป). Each Fe goes from +2 to +3 (oxidised, loses 1eโป). 5 iron atoms balance 1 manganese: 5 ร 1eโป = 5eโป.
A galvanic (voltaic) cell converts chemical energy to electrical energy via spontaneous redox reactions. An electrolytic cell does the reverse - uses electrical energy to drive a non-spontaneous reaction.
Oxidation occurs here. Negative terminal in galvanic cells. Connected to + terminal of battery in electrolytic cells.
Reduction occurs here. Positive terminal in galvanic cells. Connected to - terminal of battery in electrolytic cells.
Maintains electrical neutrality by allowing ion flow between half-cells without mixing solutions.
Carries electron flow from anode to cathode. This electron flow is the electric current.
Standard electrode potential (Eยฐ) measures the tendency of a half-reaction to occur as a reduction, relative to the standard hydrogen electrode (Eยฐ = 0.00 V).
Using electrical energy to drive a non-spontaneous redox reaction. Critical for industrial chemistry: aluminium extraction, chlorine production, electroplating, and hydrogen fuel production.
Alยณโบ ions in molten cryolite reduced at cathode. Huge energy requirement - aluminium smelting uses ~5% of UK electricity.
Electrolysis of brine (NaCl solution): Clโ at anode, Hโ at cathode, NaOH in solution. Three essential industrial chemicals from one process.
The object is the cathode. Metal ions in solution deposit onto it. Used for corrosion protection, decoration, and electrical contacts.
Electrolysis of water: 2HโO โ 2Hโ + Oโ. "Green hydrogen" when powered by renewables. Hโ is an energy carrier for fuel cells.