The name of the structure of silicates in which three oxygen atoms of $[SiO_4]^{4-}$ are shared is :-

Which one of the following is correct about the stability of the given ions?

Which of the following statements are correct?
$1.$ Charcoal can be obtained by heating wood in the absence of air.
$2.$ Charcoal is an impure form of graphite.
$3.$ Diamond is thermodynamically the most stable allotrope of carbon.
$4.$ Coke is used as an oxidising agent during the extraction of iron from its ores.

Identify $X, Y$ and $Z$ in the following reaction: $2 CH_3Cl + X \xrightarrow[570 \ K]{Y} Z$

$RCl$ $\xrightarrow[Si]{Cu \text{ powder}} R_2SiCl_2$ $\xrightarrow{H_2O} R_2Si(OH)_2$ $\xrightarrow{\text{condensation}} A$
Compound $(A)$ is:

Identify the incorrect statement about $SiO_2$ (silica) from the following.