$A$ mixture is heated with dilute $H_2SO_4$ and the lead acetate paper turns black due to the evolved gases. The mixture contains:

$M \text{ (Salt)} + \text{Dil. } HCl \xrightarrow{\text{Warm}} N \uparrow + P \downarrow$. Gas $N$ changes the colour of $FeSO_4$ solution into a yellow solution. Then,salt $M$ in the above reaction is:

The solution of a chemical compound $X$ reacts with $AgNO_3$ solution to form a white precipitate of $Y$,which dissolves in $NH_4OH$ to give a complex $Z$. When $Z$ is treated with dilute $HNO_3$,$Y$ reappears. The chemical compound $X$ can be:

Which of the following will not produce a precipitate with $AgNO_3$ solution?

Explain the brown ring test for nitrate ions.

Which salt produces a white precipitate with $AgNO_3$ solution,which becomes black on standing?