This page contains the detailed and easy notes for Edexcel IGCSE Chemistry Electrolysis for revision and understanding .

Edexcel IGCSE Paper 1: Complete Revision Summary

ELECTROLYSIS

• Electrolysis – The breaking of ionic compound by passing electricity.
• Electrolyte – The substance that undergoes Electrolysis
• Electrode – The two conducting rods dipped in an electrolyte
• Cathode – Where Cations (+ve charge ions) go. So it is negatively charge electrode
• Anions – Where anions (-ve charge ions) go. So it is positively charged.

ELECTROLYSIS OF MOLTEN IONIC COMPOUNDS

Ionic compounds conduct Electricity when in molten or in solution as the ions are free to move when they’ are in solvent or dissolved in water.

Molten Sodium Chloride

NaCl                   Na⁺(goes towards cathode) + Cl^–(goes towards anode)

Cathode                    Reduction

Na⁺ + e^–                  Na(s)

Anode                        Oxidation

2Cl^–                  Cl₂(g) + 2e^–

O – Oxidation

I – Is

L – Loss

R – Reduction

I – Is

G – Gain

ELECTROLYSIS

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ELECTROLYSIS IN SOLUTIONS

In Solution the water also gets ionized and dissociate into H+ and OH- which also competes with the ionic compounds ions to discharge.

Sodium Chloride Solution

Ions

H⁺ + OH^–

Na⁺ + Cl^–

At Cathode

2H⁺ + 2e^–                          H₂(g)

Rule – At the cathode, the element with least reacitivity will get discharged and gains electrons.

For that we have to look at the reactivity series

At Anode

2Cl^–                  Cl₂ + 2e^–

For Anode, the rule is – Halide> OH^– > other negative ions

Remaining Solution

Na⁺ + OH^–

Potassium Sulphate solution

Ions

K⁺ + SO₄^2-

H⁺ + OH^–

At Cathode

2H⁺ + 2e^–                          H₂

At Anode

4OH^–                  O₂ + 2H₂O + 4e^–

Remaining Solution

K₂SO₄

ELECTROLYSIS OF ALUMINIUM OXIDE

Bauxite an ore of aluminium is used which contains aluminium in the form of aluminium oxide.

Al₂O₃                 Al³⁺ O^2-

Bauxite is mixed with cryolite. Cryolite lowers the melting point of aluminium oxide making it melt at a lower temperature.

At Anode

2O^2-                  O₂ + 4e^–

Oxygen evolved reacts with graphite electrode forming carbon dioxide. Therefore, they are used up and needs regular replacing

At Cathode

Al³⁺ + 3e^–                          Al(s)

O₂ + C                 CO₂

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References:

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