Topics in this chapter
- Minerals and ores
- Gangue and concentration of ores
- Roasting and calcination
- Reduction of metal oxides
- Flux and slag
- Extraction according to reactivity
- Electrolytic refining
- Alloys and corrosion prevention
Key learning points
✓ An ore is a mineral from which a metal can be extracted economically.
✓ Roasting is heating in excess air; calcination is heating in limited or no air.
✓ Flux reacts with gangue to form slag.
✓ Highly reactive metals are generally extracted electrolytically.
Important equations and relations
2ZnS + 3O₂ → 2ZnO + 2SO₂ZnCO₃ → ZnO + CO₂Fe₂O₃ + 3CO → 2Fe + 3CO₂CaO + SiO₂ → CaSiO₃Multiple-choice questions
1. Unwanted earthy impurities in an ore are called:
- Flux
- Gangue
- Slag
- Alloy
Answer: B — Gangue
2. Heating a sulphide ore in excess air is:
- Calcination
- Roasting
- Refining
- Electroplating
Answer: B — Roasting
3. Flux combines with gangue to form:
- Ore
- Slag
- Alloy
- Coke
Answer: B — Slag
Very short-answer questions
- Define ore.
- What is slag?
- Name one method of refining metals.
Short-answer questions
- Differentiate between roasting and calcination.
- Explain the role of flux in metallurgy.
Long-answer question
- Describe the general stages involved in extraction and purification of a metal from its ore.