Phosphorus pentachloride in the solid state exists as:

Correct statements from the following are: $A$. Nitrogen in oxidation states from $+1$ to $+4$ disproportionates in acid medium. $B$. Nitrogen has the ability to form $d\text{--}p$ multiple bonds with itself and other elements with small size and high electronegativity. $C$. $N$-$N$ single bond is stronger than $P$-$P$ single bond. $D$. Nitrogen has highest density in its group due to small size. $E$. The maximum covalency of nitrogen is four since it has only four valence orbitals for bonding.

Explain the nature of hydride compounds of group-$15$ elements. Explain the nature of oxide compounds of group-$15$ elements. Write a note on halide compounds of group-$15$ elements.

In the Ostwald process for the manufacture of $HNO_3$,which of the following is used as a catalyst?

Which reaction does not produce ammonia?

In the reaction $4HNO_3 + P_4O_{10} \to 4HPO_3 + x$,the product $x$ is