Quick Simpler Start
You learn how electrolysis works, how metals are extracted, and how corrosion and electroplating are explained by chemistry.
When you revise this chapter, ask yourself: "Can I explain this to a friend in one easy paragraph?" If yes, you are in a good place.
Interactive Simulator
This small tool gives you a quick visual check before you move deeper into the chapter notes.
Electrolysis Predictor
Choose the setup and see which products are likely to form.
PREMIUM REVISION NOTES
ILC Higher Chemistry — Option 2B: Additional Electrochemistry
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1. Learning Objectives
- Use the electrochemical series to predict displacement and cell-voltage ideas.
- Explain electrolysis with active and inert electrodes.
- Describe electrolysis of molten lead bromide, water and copper sulfate solution.
- Explain corrosion and prevention methods.
- Describe electroplating and purification of copper.
- Explain extraction of sodium and aluminium.
- Describe transition metals, iron and steel manufacture, and environmental aspects.
2. Electrochemical Series and Cell Voltages
The electrochemical series helps predict which species are more likely to lose or gain electrons. A larger difference between two half-cells usually gives a larger cell voltage.
3. Electrolysis Basics
| Electrode | Charge | What happens |
|---|---|---|
| Cathode | Negative | Reduction: cations gain electrons |
| Anode | Positive | Oxidation: anions lose electrons |
4. Electrolysis of Molten Lead Bromide
| Electrode | Process | Product |
|---|---|---|
| Cathode | Pb2+ + 2e− → Pb | Lead metal |
| Anode | 2Br− → Br2 + 2e− | Bromine |
This is a key Higher Level example because it shows electrolysis of a molten salt clearly.
5. Electrolysis of Water and Copper Sulfate
Water
Hydrogen forms at the cathode and oxygen at the anode, in a 2:1 volume ratio.
Copper sulfate solution
With inert electrodes, copper deposits at the cathode and oxygen may form at the anode. With active copper electrodes, copper dissolves from the anode and deposits at the cathode.
| Electrode type | Main result |
|---|---|
| Inert electrodes | Cu deposited at cathode; anode reaction differs and solution composition changes |
| Copper electrodes | Copper anode dissolves, copper cathode gains mass |
6. Corrosion and Prevention
Corrosion is the gradual destruction of a metal by chemical reactions with its environment. Rusting is corrosion of iron in the presence of oxygen and water.
| Prevention method | How it works |
|---|---|
| Painting / oiling | Stops oxygen and water reaching the metal |
| Galvanising | Zinc coating protects iron |
| Sacrificial protection | A more reactive metal corrodes instead |
| Electroplating | Protective metal layer added |
7. Electroplating and Copper Purification
Electroplating
An object is made the cathode and coated with a thin layer of another metal.
Purification of copper
| Part | Role |
|---|---|
| Impure copper anode | Dissolves as Cu2+ |
| Pure copper cathode | Gains copper deposit |
| Copper sulfate electrolyte | Provides Cu2+ ions |
8. Extraction of Sodium and Aluminium
Sodium
Sodium is extracted by electrolysis of molten sodium chloride because it is too reactive to be extracted by carbon reduction.
Aluminium
Aluminium is extracted by electrolysis of molten aluminium oxide dissolved in cryolite.
Cryolite lowers the melting point and reduces energy cost.
9. Transition Metals, Iron and Steel
d-block / transition metals
Transition metals often show variable oxidation states, coloured compounds and catalytic behaviour.
Iron and steel manufacture
Iron is extracted in the blast furnace, then refined to make steels with different properties.
| Material | Main point |
|---|---|
| Iron | Extracted from ore by reduction in the blast furnace |
| Steel | Produced by controlling carbon and other alloying elements |
Environmental aspects
Iron and steel manufacture use a lot of energy and can release CO2 and other pollutants, so efficiency and pollution control matter.
10. Last-Minute Revision Sheet
- Know molten lead bromide electrolysis.
- Know the difference between active and inert electrodes.
- Know corrosion and its prevention methods.
- Know electroplating and copper purification.
- Know why sodium and aluminium need electrolysis for extraction.
- Know transition-metal features and iron/steel links.
11. Self-Assessment Checklist
- I can use the electrochemical series to predict reactions.
- I can describe molten lead bromide electrolysis.
- I can compare active and inert electrodes.
- I can explain corrosion and prevention methods.
- I can describe copper purification and electroplating.
- I can explain sodium and aluminium extraction.
- I can link transition metals to iron and steel manufacture.