Class 8, Science, Chapter-11, Lecture-2, Electrolysis (Notes)
ELECTROLYSIS:
The chemical decomposition produced by passing an electric current through an electrolyte solution is called electrolysis.
ELECTROLYSIS of Water:
The chemical decomposition of water into Hydrogen and Oxygen produced by passing an electric current through acidified or alkaline water is called electrolysis of water.
$${{\rm{WATER}}\mathrel{\mathop{\kern0pt\longrightarrow}
\limits_{Chemical{\rm{ }}{\mathop{\rm Re}\nolimits} action}^{Electric{\rm{ }}Current}} \mathop {{\rm{HYDROGEN}}}\limits_{{\rm{(Cathode)}}} + \mathop {{\rm{OXYGEN}}}\limits_{{\rm{(Anode)}}} }$$
In the process:
- One Graphite rod acts as Anode ( +ve )
Another Graphite rod acts as Cathode ( –ve )
Acidified water acts as electrolyte. - Oxygen Gas is formed at Anode
- Hydrogen Gas is formed at Cathode
ELECTROPLATING:
The process of depositing a thin layer of a desired metal over a metallic object with the help of electric current is called electroplating.
In the process:
- Metal to be deposited acts as anode ( +ve )
Metallic Object acts as cathode ( –ve )
Solution of the Salt of the metal to be deposited act as electrolyte. - Metal at anode becomes positive ions an goes to the electrolyte
- Positive metal ions from electrolyte goes to the Cathode.
- Ions of Desired metal becomes atoms and gets deposited over the metallic object at cathode
ELECTROLYTIC REFINING:
The purification of impure metal by electrolysis of metal salt in which impure metal acts as anode and pure metal acts as cathode is called electrolytic refining.
- used for copper, gold, zinc, chromium, nickel
In the process:
- Impure metal acts as anode ( +ve )
Pure metal acts as cathode ( –ve )
Metal salt solution act as electrolyte. - Pure metal is deposited at cathode
- More reactive metals pass into the solution
- Less reactive metals fall at the bottom as ANODE MUD