Which of the following combinations does not liberate $NH_3$ gas?

Which one of the following elements occurs free in nature?

Write a balanced chemical equation for the reaction of $PCl_5$ with water.

In group $-15$,as we move from $N$ to $Bi$,the $M_2O_3$ type oxides become ...... .

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:

$P_4 O_{10}$ is the anhydride of