In a Lassaigne's test for sulphur in an organic compound,the purple colour formed with sodium nitroprusside solution is due to the formation of:

Given below are two statements :
Statement $I :$ In Lassaigne's test,the covalent organic molecules are transformed into ionic compounds.
Statement $II :$ The sodium fusion extract of an organic compound having $N$ and $S$ gives prussian blue colour with $FeSO_4$ and $FeCl_3$.
In the light of the above statements,choose the correct answer from the options given below.

Why is it necessary to use acetic acid and not sulphuric acid for acidification of sodium extract for testing sulphur by lead acetate test?

Lassaigne's test for nitrogen is negative for which compound?

An organic compound on heating with $CuO$ produces $CO_{2}$ but no water. The organic compound may be

In the detection test of nitrogen,the Prussian blue colour is due to which compound?