Electrolysis of Silver Sulphate

Electrolysis of Silver/Argentum Sulphate solution, Ag2SO4

+

Carbon electrode

Anode

Cathode

Silver sulphate solution OH-, SO42-

Ag+, H+

Ions present in the electrolyte: Cation: Ag+, H+. Anion: OH-, SO42Ions move to anode: OH-, SO42Ion choose to be discharged at anode: OH- (position of ions) Half equation: 4OH-  O2 + 2H2O + 4e Observation: Bubbles of colourless gas released. Ions move to cathode: Ag+, H+. Ions choose to be discharged at cathode: Ag+ (position of ions) Half equation: Ag+ + e  Ag Observation: Silver metal deposited at the electrode.

Electrolysis of 3.0 M (concentrated) Potassium Bromide solution, KBr 

+

Carbon electrode

Anode

Cathode

3.0 M potassium  bromide OH-, Br -

K +, H+

Ions present in the electrolyte: Cation: K +, H+. Anion: OH-, Br Ions move to anode: OH-, Br Ion choose to be discharged at anode: Br - (concentrated ion) Half equation: 2Br -  Br 2 + 2e Observation: Bubbles of brownish gas released. Ions move to cathode: K +, H+. Ions choose to be discharged at cathode: H+ (position of ions) Half equation: 2H+ + 2e  H2 Observation: Bubbles of colourless gas released

Electrolysis of Silver nitrate solution, AgNO3 with silver plate.

+

Silver electrode

Anode

Cathode

Silver Nitrate solution OH-, NO3-

Ag+, H+

Ions present in the electrolyte: Cation: Ag+, H+ Anion: OH-, NO3Ions move to anode: OH-, NO3Ion choose to be discharged at anode: No ion discharged. Anode is silver metal, which is an active anode. It will dissolve in the electrolyte. Half equation: Ag  Ag+ + e Observation: The silver electrode becomes thinner  Ions move to cathode: Ag+, H+. Ions choose to be discharged at cathode: Ag+ (position of ions) Half equation: Ag+ + e  Ag Observation: Silver metal deposited at the electrode. Carbon electrode becomes thicker. The colour of the solution remains unchanged.

Application Of electrolysis in Industries Extraction of metals

Carbon electrodes + Anode - Cathode Carbon lining Molten aluminium oxide, Al 2O3 Al3+ , O2Molten aluminium Aluminium ions in the electrolyte will be discharged at the carbon electrodes and  become aluminium atom. Molten aluminium will be collected at the bottom.

Oxide ions, O2- in the electrolyte will be discharged at the carbon lining and become oxygen gas. 2O2-

Al3+ + 3e  Al

2. Purification of metals

+ Anode

Impure copper 

Impurities



O2 + 2e

Cathode

Pure/Tulen/Asli copper 

Copper (II) sulphate solution Cu2+ , H+, SO42- , OH-

The impure copper plate dissolves to form Cu2+ ions. Cu  Cu2+ 2e The impurities fall to the bottom of the beaker. The Cu2+ ions are discharged to form copper at the pure copper plate. Cu2+ + 2e  Cu

3. Electroplating of metals Penyaduran logam

+

Anode

Cathode

Iron spoon (sudu besi)

Copper electrode

Copper (II) sulphate solution Cu2+ , H+, SO42- , OHThe copper anode dissolves to form Cu2+ ions. Half equation: Cu  Cu2+ 2e At the cathode, Cu2+ ions are discharged and deposited on the surface of  the iron spoon. Half equation: Cu2+ + 2e  Cu Condition for good quality of plating: Concentration of Cu2+ ions must be low The electric current must be small The iron spoon must be turned steadily The surface of iron spoon must be clean.

CATION

Half reaction

K + (Potassium) K + + e  K   Na+ (Sodium) Na+ + e  Na Ca2+ (Calcium) Ca2+ + 2e  Ca Mg2+ (Magnesium) Mg2+ +2e  Mg Al3+ (Aluminium) Al3+ + 3e  Al Zn2+ (Zinc) Zn2+ + 2e  Zn Fe2+ (Iron) Fe2+ + 2e  Fe Sn2+ (Stanum) Sn2+ + 2e  Sn Pb2+ (Lead) Pb2+ + 2e  Pb H+ (Hydrogen) 2H+ + 2e  H2 Cu2+ (Copper) Cu2+ + 2e  Cu Ag+ (Silver) Ag+ + e  Ag

ANION

Half Reaction

F- (Fluoride) 2 F-  F2 + 2e SO42- (Sulphate) SO42-  SO2 + O2 + 2e  NO3- (Nitrate) 2NO3-  2NO2 + O2 + 2e Cl- (Chloride) 2Cl-  Cl2 + 2e Br - (Bromide) 2Br-   Br 2 + 2e I- (Iodide) 2I-  I2 + 2e OH- (hydroxide) 4OH-  O2 + H2O + 4e