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.