Which nitrogen trihalide is the least basic?

The element that does $NOT$ exhibit allotropy is$-$

Phosphorus forms a number of oxoacids. Out of these oxoacids,phosphinic acid $(H_3PO_2)$ has strong reducing properties. Write its structure and also write a reaction showing its reducing behavior.

Superphosphate is the mixture of

Identify the reaction which does not liberate $N_2$.

The action of concentrated nitric acid $(HNO_3)$ on metallic tin $(Sn)$ produces: