ELECTROLYSIS IN IDUSTRY EXTRACTION OF METALS PURIFICATION OF METALS ELECTROCHEMISTRY ELECTROLYSIS MOLTEN COMPOUNDS AQUEOUS SOLUTION ELECTROLYSIS IN IDUSTRY EXTRACTION OF METALS PURIFICATION OF METALS ELECTROPLATING OF METALS VOLTAIC CELL ELECTROCHEMICAL SERIES

ELECTROCHEMISTRY

ELECTROCHEMISTRY

Substance that can conduct electricity in molten/ aqueous solution Process-a compound is decomposed into its constituents elements when electric current passes through an electrolyte ELECTROLYSIS Substance that can conduct electricity in molten/ aqueous solution Undergo chemical changes ELECTROLYTE Conductors in the form of wires, rods, or plates. It passes electricity through the electrolyte during electrolysis Inert: do not take part in chemical reactions e.g: carbon & platinum Active : take part in chemical reaction e.g: copper, silver, mercury Cathode: negative terminal Anode: positive terminal ELECTRODE

ELECTROLYSIS SETUP -molten compound-

Terms in electrolysis Cation Anion Electrode Inert electrode Battery Positive terminal Negative terminal Cathode Anode Electrolysis Molten Aqueous Electrolyte Non-electrolyte Discharged

anion cation

ELECTROLYSIS OF AQUEOUS SOLUTIONS + Aqueous solution A compound water NaCl solution (aq) NaCl (s) Cation Na⁺ H⁺ Anion Cl⁻ OH⁻

Electrolysis of NaCl solution Anode: 4OH⁻  O2 + 2H2O + 4e⁻ Cathode: 2H⁺ +2e⁻H2 C A R B O N C A R B O N Cl⁻ Na⁺ OH⁻ H⁺ e⁻ Na⁺ Cl⁻ H⁺ OH⁻

Factors for selective discharge Positions of ions in electrochemical series Concentration of the ions in the electrolyte Types of electrodes used in the electrolysis

Electrolytic cell

Electrochemical series (ECS) D C H G The lower the position of an ion in ECS,the higher is the tendency of the ion to be discharged.

Mari menghafal… F..............Fasha SO............sandha K.................kalau Na...............nak Ca.........cari Mg...............mak Al..................ali Zn.................ziarah Fe..................flat Sn..................satu Pb..................pada H.................Hari Cu............Cuti Au..................ahad F..............Fasha SO............sandha NO............Nok K...............Kahwin B...............Budak I................India OH............OH!

Example: Example 1: 0.5 mol dm3 of potassium chloride, KCl solution Cations : K+ and H+ Anions : Cl-and OH- Cathode (negative electrode): H+ move to the cathode (ions are selectively discharge) Anode (positive electrode): OH- move to the anode (ions are selectively discharge)

Example 2: 0.1 mol dm3 of copper(II) sulphate, CuSO4 solution Positive ions (cations): copper ions (Cu2+) and hydrogen ions (H+) Negative ions (anions): sulphate ions (SO42-) and hydroxide ions (OH-) Cathode (negative electrode): Cu2+ move to the cathode (ions are selectively discharge) Anode (positive electrode): OH- move to the anode (ions are selectively discharge)

Concentration of Ions in electrolyte Ion that have high concentration in electrolyte will be discharged.

Electrolysis 2.0 mol dm-3 of lead(II) bromide, PbCl2 solution Cathode: 2H⁺ +2e⁻H₂ Anode: 2Cl⁻ Cl2+ 2e⁻ C A R B O N C A R B O N if 2 ions are placed very far apart in the ECS, the concentration aspect become insignificant. Cl⁻ Pb2⁺ OH⁻ H⁺ Pb2 Cl⁻ H⁺ OH⁻

Inert electrodes: Carbon and platinum (Both of these electrodes do not react with the electrolytes or products of electrolysis) Active electrodes: Silver, copper and nickel (Active anode ionizes and concentration of cations in the electrolyte does not change)

Electrolysis of CuSO4 Cathode: Anode: Cu2⁺ +2e⁻Cu CuCu2⁺ + 2e⁻ c o p OH⁻ H⁺ Cu2⁺ SO42⁻ H⁺ OH⁻