The element not present in Nessler's reagent is:

Nessler's reagent is

In the mustard oil reaction,an amine is treated with

$A$ compound $Z$ with molecular formula $C_3H_9N$ reacts with $C_6H_5SO_2Cl$ to give a solid,insoluble in alkali. Identify $Z$.

$1^o$ amine and $2^o$ amine can be differentiated by

An aromatic compound "$A$" on treatment with $Zn / NH_4Cl$ and subsequent heating with ammoniacal silver nitrate solution gives a black precipitate. Which functional group does "$A$" contain?