Silicon-Compounds
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| Discuss Silicon-Compounds COMPOUNDS OF SILICON
- SILICONES
Silicones are synthetically polymerised organo-silicon polymers. These are charecterised by -Si-O-Si-O-Si-O-… linkages along with -C-C-C-C-… linkages present as side chains.
TYPES OF SILICONES
Silicones may be of the following types
- linear silicones ( straight chained)
- cyclic silicones
- cross linked silicones ( three dimensional)
PROPERTIES
- The lower silicones are oily liquids, but the higher members containing long chains or ring structures are waxy and rubbery solids.
- Silicones are highly stable towards heat and chemical reagents.
- Silicones are not wetted by water and thus are water repellant.
- Are non-toxic and chemically inert.
- The viscosity of silicon oils remains constant with the change of temperature and silicones do not thicken in cold weather.
USES
- Used as a low temperature lubrication.
- Used for high temperature oil baths and high vacuum pumps.
- Used in making water proof cloths.
- Used as insulating material.
- Mixed in paints and enamels to make them resistant to th eeffects of high temperature and damp.
- SILICON CARBIDES
- It is colour less
- Very hard
- Relative density 3.217
- Melting point 2700OC
- Chemically inert and resists the attack of almost all reagents except fused caustic soda.
- Its structure is similar to that of diamond.
Silicon carbide is a black solid compound. It is represented by SiC and is called carborundum. It is charecterised by
PREPARATION
It is prepared by strongly heating a mixture of sand, carbon, common salt and sawdust in an electric furnace.
SiO2 + 3C è SiC + 2CO
USES
- Because of its hardness it is widely used as an abrasive
- Used in the lining of furnaces
- Used as a deoxidant in metallurgy
- As a resistor for electric furnaces
