First ionisation enthalpy values of first four group $15$ elements are given below. Choose the correct value for the element that is a main component of apatite family $:$

Pure $N_2$ is obtained by:

Phosphine is prepared by the reaction of $P_4$ with which of the following?

Which of the following reacts with $Fe(II)$ ions to form a brown complex?

Identify the incorrect statements about group $15$ elements :
$A$. Dinitrogen is a diatomic gas which acts like an inert gas at room temperature.
$B$. The common oxidation states of these elements are $-3, +3$ and $+5$.
$C$. Nitrogen has unique ability to form $p\pi-p\pi$ multiple bonds.
$D$. The stability of $+5$ oxidation states increases down the group.
$E$. Nitrogen shows a maximum covalency of $6$.
Choose the correct answer from the options given below.

The chemical used for cooling in refrigeration is