Why can't ammonium nitrite be used to prepare nitrogen gas?

How do we find the answer?

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.

Solubility would be your answer.

13) a 14) a15) b16) i don't know sorry17) a (maybe)