In which of the following is the $P - O - P$ bond present?

On adding water to $BiCl_3$ solution in $HCl$,the compound produced is

White phosphorus contains

Why is $N_2$ less reactive at room temperature?

In some of the reactions,thallium resembles aluminium,whereas in others,it resembles group $1$ metals. Support this statement by giving some evidence.

$HNO_3 + P_4O_{10} \rightarrow HPO_3 + A$; the product $A$ is