Silicones are organo – silicon polymers containing Si – O – Si linkages. These are formed by the hydrolysis of alkyl or aryl substituted chlorosilanes and their subsequent polymerisation.
R2SiCl2 gives rise to straight chain linear polymers
RSiCl3 gives a complex cross linked polomer
These polymers are used in water proofing textiles in glassware, as lubricants and anti foaming agents.
Silicon Carbide (Carborundum), SiC
It is obtained when a mixture of sand, carbon common salt and saw dust is strongly heated in an electric furnace
SiO2 + 3C —> SiC + 2CO
It is chemically inert and resists the attack of almost all the reagents. It is used as an abrasive to make grind stones knife sharpness, etc.
Illustration : What is etching of glass ? How does to happens?
Solution: Glass is chemically attacked by HF
This is known as etching of glass due to corrosive action of HF
Na2SiO3 + 6HF —> 2NaF + SiF4 + 3H2O
CaSiO3 + 6HF —> CaF2 SiF4 + H2O
SiF4 + 2HF —> H2SiF6