$A$ gas at low temperature does not react with most compounds. It is almost inert and is used to create an inert atmosphere in bulbs. The combustion of this gas is exceptionally an endothermic reaction. Based on the given information,we can conclude that the gas is

What is the chemical formula of hypophosphorus acid?

What is formed when $PCl_3$ reacts with water?

Given below are two statements:
Statement $I$: The halogen that makes the longest bond with hydrogen in $HX$ has the smallest covalent radius in its group.
Statement $II$: $A$ group $15$ element's hydride $EH_3$ has the lowest boiling point among corresponding hydrides of other group $15$ elements. The maximum covalency of that element $E$ is $4$.
In the light of the above statements,choose the correct answer from the options given below.

Pure $N_2$ is not produced when

$P_4O_{10}$ is not used to dry $NH_3$ gas because