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USAGE OF METALS
Usage of metals
ALLOYS
Alloy is a solid solution or homogeneous mixture of two or more elements at least one of which is a metalIt usually has different properties than those of its components
Properties of alloys:
1. They are usually powder than pure metals2.They are poorer conductor of electricity and heat than pure metals3.They have high resistance to corrosion
Iron alloys:
• Cast iron• Steel
Cast iron is an alloy consisting mostly of iron with carbon from 2% to 4,5% by weight, and also Mn, Si, P and S. Cast iron harder than iron and very brittle
METAL ORES
Rocks from which metals are obtained are called as ores
Extracting metals from their ores
Native metals: unreactive metals like Au, Ag, Pt and Cu are found as elements
The metal is obtained only by separating it from impurities, just by removing stones from soil
Extraction by removing oxygen
Metal oxides are reduced by such reducing agents as C, CO, Al, or by electrolysis
Reduction by electrolysis
Metals such as Na, K, Mg, Ca have to be freed from their ores by electrolytic processes, since they are active metals.
Pyrometallurgy is obtaining metals from minerals and metallurgical ores byn thermal reactions
heat2PbS + 3O2 → 2PbO + 3SO2 ↑
heatPbO + H2 → Pb + H2O
heatWO3 + 3H2 →W + 3H2O
heatTiCl4 + 2 Mg → Ti + MgCl2
Hydrometallurgy involves the use of aqueous solutions to extract metals or compounds from their ores. CuO + H2SO4 → CuSO4 + H2OCuSO4 + Fe → FeSO4 + Cu
By this method Ag, Au, Zn, Mo obtained.