Question

Electrolysis of alumina is done. Write chemical equation for the event.

Answer 1

In the Electrolysis of the Alumina, three compounds are used. They are ⇒

1. Alumina.
2. Cryolite.
3. Flourspar.

The Dissociation reaction are ⇒

 Al₂O₃ -----------→  2Al³⁺ + 3O²⁻
Na₃AlF₆ ---------→ 3Na⁺ + Al³⁺ + 6F⁻
CaF₂ -----------→ Ca²⁺ + 2F⁻


Now, out of these metals, only the aluminum enters the cathode since it lies below the Calcium and the Sodium. 

   At Cathode ⇒ Al³⁺ + 3e⁻ ---------→ Al

At anode only oxygen enters, 

 At Anode ⇒ O²⁻ - 2e⁻ ----------------→ O
 O + O ---------→ O₂

This oxygen reacts with the Carbon (or Anode) and forms Carbon dioxide. 

 C + O₂ ------------→ CO₂


Hope it helps.

Answer 2

Answer:

The electrolysis of alumina is carried out in a steel tank lined inside with graphite. The graphite lining serves as cathode. Anode is also made up of graphite rods hanging in the molten mass. The electrolyte consists of alumina dissolved in fused Cryolite (Na3AIF6) and Fluorspar (CaF2). Cryolite lowers the melting point of alumina and fluorspar increases the fluidity of the mass so that the liberated aluminum metal may sink at the bottom of the cell. When electric current is passed through this mixture, the aluminum is collected at the cathode in molten state and sinks at the bottom.

Ionization of Alumina : 2AI2O3 ➝ 6O-² + 4AI+³

Reaction at Cathode : 4AI+³ + 12e- ➝ 4AI

Reaction at Anode : 6O-² ➝ 3O2 + 12e-, C + O2 ➝ CO2

Explanation:

I hope it will help you...✍