Concentrated $HNO_3$ turns brown on standing due to the formation of:

Which of the following is a good oxidising agent?

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.

The total number of paramagnetic gaseous products formed in all the following reactions $[A + B + C ]$:
$(A)\ NH_4 NO_3 \xrightarrow{\Delta} \text{Products}$
$(B)\ 3 NaNO_2 + 3 H_2 SO_4 \longrightarrow \text{Products}$
$(C)\ Pb(NO_3)_2 \xrightarrow{673 \ K} \text{Products}$

Which of the following is an ionic compound?

Which one of the following hydrides is least stable?