$NH_3 + O_2 \xrightarrow[500 \ K]{Pt} A + H_2O$
$A + O_2 \to B$; $B + H_2O \to C + A$
$A, B$ and $C$ respectively are

Which of the following represents the correct order of acidic strength?

The possible oxidation states of $Tl$ are

The reaction of zinc with dilute and concentrated nitric acid,respectively,produces:

With excess of water,$PCl_5$ gives

Which of the following statements are correct?
$(I)$ $P_4$ molecule is very reactive because of angular strain.
$(II)$ The basicity of $H_3PO_3$ is $3$.
$(III)$ In gas phase,all $P-Cl$ bonds of $PCl_5$ have same bond length.
$(IV)$ In solid state,$PCl_5$ exists as an ionic solid,in which anion $[PCl_6]^-$ has octahedral and cation $[PCl_4]^+$ has tetrahedral shape.