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Sunday, August 14, 2011

Chemistry X- Occurrence of Metal and Non Metal

OCCURRENCE OF METALS
The earth’s crust is the major source of metals. Seawater also contains some soluble salts such as sodium chloride, magnesium chloride, etc.
The elements or compounds, which occur naturally in the earth’s crust, are known as minerals.
At some places, minerals contain a very high percentage of a particular metal and the metal can be profitably extracted from it. These minerals are called ores.
Metals like titanium, chromium, manganese, zirconium etc. find their applications in the manufacture of defence equipments. These are called strategic metals.
The metal uranium plays, a vital role in nuclear reactions releasing enormous energy called nuclear energy. Copper, silver and gold are called coinage metals as they are used in making coins, jewellery etc
Minerals: A mineral may be a single compound or complex mixture of various compounds of metals which are found in earth.
Ores: The mineral from which a metal can be readily and economically extracted on a large scale is said to be a ore.  E.g. For example, clay (Al2O3.2SiO2.2H2O) and bauxite (Al2O3.2H2O) are the two minerals of aluminium. But aluminium can be profitably extracted only from bauxite.
Hence bauxite is an ore of aluminium and clay is its mineral.
Differences between minerals and ores
 Minerals contain a low percentage of metal while ores contain a large percentage of metal.
 Metals cannot be extracted easily from mineral. On the other hand, ores can be used for the extraction of metals.
Mining: The process of extracting the ores from the earth crust is called mining.
Metallurgy: Various steps involved in the extraction of metals from their ores as well as refining of crude metal are collectively known as metallurgy.
Gangue or Matrix: The rocky impurity, associated with the ore is called gangue or  Matrix.
Flux: It is a compound added to the ore to remove its impurities by fusion .eg. CaO
Slag: It is the fusible product formed when flux reacts with gangue during the extraction of metals. Flux + Gangue → Slag
Smelting : Smelting is the process of reducing the roasted oxide to metals in the molten condition.
Enrichment of ores: - It is done to remove earthy impurities like clay, sand etc. from an ore is called enrichment or concentration of the ore. 

Oxide Ores
Carbonate Ores
Halide Ores
Sulphide Ores
Bauxite(Al2O3.2H2O)
Cuprite(Cu2O)
Haematite (Fe2O3)
Marble (CaCO3)
Magnesite (MgCO3)
Siderite (FeCO3)
Cryolite (Na3AlF6)
Fluorspar (CaF2)
Rock salt (NaCl)
Galena (PbS)
 Iron pyrite  (FeS2)
 Zinc blende   (ZnS)

1 comment:

Fullmarks Publications said...

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