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Electrolysis, Golden Rules, Electrolysis of molten compounds - Coggle…
Electrolysis
Electrodes
Definition
Rod for current flow
Types
Inert ( Graphite and Platinum )
Active (other metals)
Anode (positive)
Connected to positive pole
Attracts Anions (negative ions)
Oxidation occurs her (AN OX)
Cathode (negative)
Connected to negative pole
Attracts Cations (positive ions)
Reduction occurs here (RED CAT)
Electrolysis of aqueous solutions
Water Present: H2O ⇌ H+ + OH– ions
Concentration Types
Diluted (More water, less salt)
Concentrated (Less water, more salt)
Anode Selection Rule (Oxidation)
Takes more available negative ion
In a dilute solutions , OH- is always attracted
4OH- → 2H2O + O2 + 4e-
Cathode Selection Rule (Reduction)
Takes less reactive positive ion (Check reactivity series)
Conc. NaCl (Brine)
Cathode Product: H2
Anode Product: Cl2
Electrolyte Change: Becomes alkaline NaOH
Aqueous CuSO4
Cathode Product: Cu (Pinkish brown solid)
Anode Product: O2
Electrolyte Change: Becomes H2SO4; Blue color fades
Diluted H2SO4
Cathode Product: H2
Anode Product: O2
Definitions and Fundamentals
Definition
The decomposition of an ionic compound when molten or aqueous solution by passage of an electric current
Nature of reaction
Redox
Endothermic
Electrolyte
Is an ionic compound in a molten or dissolved solution that conducts the electricity
Applications of Electrolysis
Active Electrode System
Example: Aqueous CuSO4 (Copper Electrodes)
Anode Thins: Cu(s) → Cu2+(aq) + 2e (Dissolving)
Cathode Thickens: Cu2+(aq) + 2e → Cu(s) (Deposition)
Used in Copper Purification
Electroplating (Cathodic Protection)
Definition: Coating one metal object with another
Objective 1: Resistance to corrosion/damage (e.g., Cr, Ni plating)
Objective 2: Improve appearance (e.g., Ag plating cutlery)
Setup Requirements
Anode: Metal to plate with
Cathode: Object to be plated
Electrolyte: Solution containing metal ions (e.g., Silver nitrate)
Golden Rules
PANIC : Positive Anode , Negative is Cathode
AN OX / OIL : Anode Oxidation / Oxidation is loss of electrons
RED CAT / RIG : Reduction at Cathode / Reduction is Gain of electrons
Electrolysis of molten compounds
Molten Lead(II) Bromide(PbBr2)
Half equation at Cathode : Pb2+ + 2e ----> Pb
Half equation at anode : 2Br ----> Br2 + 2e-
Electrolyte is used up
Aluminum Extraction
Cannot be extracted by carbon reduction (Al is above C in reactivity)
Ore : Bauxite (Al2O3 + Fe2O3)
Purification Step: Bauxite treated with NaOH to get pure Alumina (Al2O3)
Electrolyte setup
Alumina dissolved in molten cryolite
cryolite lowers melting point (saves energy)
cryolite increase conductivity
Cathode Reaction: Al3+ + 3e → Al (Reduction)
Anode Reaction: 2O2- → O2 + 4e- (Oxidation)
Anode Problem: O2 reacts with Carbon anode forming CO2