Explain the structure of silica. How does it react with
NaOH.

Explanation

`to` Silica is a giant molecule with 3-dimensional structure.
`to` In Silica eight membered rings are formed with alternate Silicon and Oxygen atoms:
Each .Si. is tetrahedrally surrounded by four Oxygen atoms.
`to` Each Oxygen at the vertex of the tetrahedron is shared by two Silicon atoms.
`to` In `SiO_(2)` Silicon atom under goes `sp^(3)` hybridisation.
a) Silica reacts with NaOH and forms sodium Silicate `(Na_(2)SiO_(8))`
`SiO_(2)+2NaOH to Na_(2)SiO_(3)+H_(2)O`
b) `SiO_(2)` Treated with HF to form `SiF_(4)` .Which on hydrolysis to form `H_(4)SiO_(4)` and `H_(2)SiF_(6)`
`SiO_(2)+4HG to SiF_(4)+2H_(2)O`
`SiF_(4)+4H_(2)OtoH_(4)SiO_(4)+2H_(2)SiF_(6)`