When orthoboric acid is heated,the residue left is ...

In the following reaction,assign the correct category for the underlined atom in the product of complete hydrolysis at $R.T.$:
$\underline{I}Cl_3 + H_2O \longrightarrow HIO_2 + HCl$

In the reaction $B_2O_3 + C + Cl_2 \to A + CO$,the $A$ is:

Boric acid is not used in which of the following?

Match the species given in Column-$I$ with properties given in Column-$II$.

Column-$I$	Column-$II$
$A$. Diborane	$1$. Used as a flux for soldering metals
$B$. Gallium	$2$. Crystalline form of silica
$C$. Borax	$3$. Banana bonds
$D$. Alumino silicate	$4$. Low melting,high boiling,useful for measuring high temperatures
$E$. Quartz	$5$. Used as catalyst in petrochemical industries

$BCl_3$ and $AlCl_3$ exist in $:-$