Find the non-semiconductor element among the following.

In the following reaction,assign the product of complete hydrolysis at $R.T.$ for the underlined atom:
$\underline{Si}O_2 + H_2O \longrightarrow $ No reaction

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

Which of the following is $NOT$ a polymorphic form of silica $(SiO_2)$?

$A$ black sulphide precipitate when treated with ozone becomes white. The white compound is:

Find $A$,$B$ and $C$ in the following reactions:
$NH_3 + A + CO_2 \rightarrow (NH_4)_2CO_3$
$(NH_4)_2CO_3 + H_2O + B \rightarrow 2NH_4HCO_3$
$NH_4HCO_3 + NaCl \rightarrow NH_4Cl + C$