Electrochemistry

 
6.1 Electrolytic Cell
 

1. Electrochemistry: a study in chemistry of the relationship between electrical and chemical phenomena like those occuring in 2 types of electrochemical cells

  • Electrolytic cell
  • Chemical cell

2. Electrolysis: the decompositiion of a compound in the molten or aqueous state into its constituent elements when electric current flows through it

3. Electrlytic cell is made up of 

  • Battery
  • Anode
  • Cathode
  • Electrolyte

4. During the electrolysis process,

  • cations move to the cathode
  • anions move to the anode

5. Factors affecting the products in electrolysis

  • Position of ions in the electrochemical series
 

Cation 

Potassium ion

Sodium ion

Calcium ion

Magnesium ion

Aluminium ion

Zinc ion

Iton(II) ion

Tin ion

Lead(II) ion

Hydrogen ion

Copper(II) ion

Silver ion

Ease of discharge increases

Anion

Fluoride ion

Sulphate ion

Nitrate ion

Chloride ion

Bromide ion

Iodine ion

Hydroxide ion

 
  • Concentration of electrolyte
    • The concentration of ions in an electrolyte affects the selection of ion to be discharged
  • Type of electrode
    • If the metal is used as the anode is the same as the metal ion in the electrolyte:
      • the metal ions will discharge to form atoms of the metal when it deposited at the cathode
      • the concentration of metal ions in the electrolyte does not change
    • if the type of substance used as the anode is not the same as the type of metal ion in the electrolyte:
      • the atoms of the anode do not dissolve in the electrolyte and negative ions in the electrolyte are discharged at the anode
      • the less electropositive ion will be discharged at the cathode

6. Application of electrolysis in industries

  • Extraction of metals
  • Purification of metals
  • Electroplating of metals
  • Wastewater treatment using electrocoagulation 
 
6.2 Chemical Cell
 

1. Simple chemical cell is made up of 2 different metals immersed in an electrolyte and connected to an external circuit with connecting wires

2. The polarity of the cell depends on the positions of the 2 metals in the reactivity series