Bleaching powder loses its power on keeping for a long time because

$PbO_2$ reacts with concentrated $HNO_3$. The gas evolved is:

The formation of $Al_2O_3$ involves the evolution of a large quantity of heat,which makes its use in:

Choose the correct statements about allotropes of carbon:
$I$. Graphite has a layered structure.
$II$. Buckminsterfullerene is not aromatic in nature.
$III$. The distance between two adjacent layers in graphite is $340 \ pm$.
$IV$. The hybridization of carbons in graphite and Buckminsterfullerene is the same $(sp^2)$.

Silicon is an important constituent of

$Ge(II)$ compounds are strong reducing agents,whereas $Pb(IV)$ compounds are strong oxidizing agents. This is due to: