The reaction of $NO$ with $N_2O_4$ at $250 \ K$ gives :

How many $H-$ atoms are directly bonded to the phosphorus atom in hypophosphorous acid?

In the following reaction,identify the nature of the product formed by the complete hydrolysis of the underlined atom at $R.T.$:
$\underline{N}F_3 + H_2O \longrightarrow \text{No reaction}$

Which compound is used in smoke screens?

In the Ostwald's process for the manufacture of $HNO_3$,the catalyst used is

Match $List-I$ with $List-II$,match the gas evolved during each reaction.

$List-I$	$List-II$
$A$. $(NH_4)_2Cr_2O_7 \xrightarrow{\Delta}$	$I$. $H_2$
$B$. $KMnO_4 + HCl \rightarrow$	$II$. $N_2$
$C$. $Al + NaOH + H_2O \rightarrow$	$III$. $O_2$
$D$. $NaNO_3 \xrightarrow{\Delta}$	$IV$. $Cl_2$

Choose the correct answer from the options given below.