Ammonia gas is dried by using ...........

Pure concentrated $HNO_3$ makes iron passive as the surface is covered with a protective layer of:

In which oxidation state,group $15$ elements act as Lewis base?

Which of the following elements does not show allotropy?

The following are some statements related to $VA$ group hydrides:
$I$. Reducing property increases from $NH_3$ to $BiH_3$.
$II$. Tendency to donate lone pair decreases from $NH_3$ to $BiH_3$.
$III$. Thermal stability of hydrides decreases from $NH_3$ to $BiH_3$.
$IV$. Bond angle of hydrides decreases from $NH_3$ to $BiH_3$.
The correct statements are:

Reaction of zinc with cold and very dilute nitric acid yields