What is meant by $Tin \ Plague$?

Rationalise the given statements and give chemical reactions:
$1$. Lead $(II)$ chloride reacts with $Cl_2$ to give $PbCl_4$.
$2$. Lead $(IV)$ chloride is highly unstable towards heat.
$3$. Lead is known not to form an iodide,$PbI_4$.

Which non-metals have high melting and boiling points? State them.

The effective component of bleaching powder is $.....$ of calcium.

Match the items in Column $I$ with its main use listed in Column $II$.

Column $I$	Column $II$
$A$. Silica gel	$i$. Transistor
$B$. Silicon	$ii$. Ion-exchanger
$C$. Silicone	$iii$. Drying agent
$D$. Silicate	$iv$. Sealant

Philosopher's wool when heated with $BaO$ at $1100 \ ^oC$ gives the compound