White precipitate of $AgCl$ dissolves in aqueous ammonia solution due to formation of $.....$ .

The active substance in Nessler's reagent used for the detection of ammonia is ..........

$A$ solution containing $2.675 \ g$ of $CoCl_3 \cdot 6 NH_3$ (molar mass $= 267.5 \ g \ mol^{-1}$) is passed through a cation exchanger. The chloride ions obtained in solution were treated with excess of $AgNO_3$ to give $4.78 \ g$ of $AgCl$ (molar mass $= 143.5 \ g \ mol^{-1}$). The formula of the complex is
(At. mass of $Ag = 108 \ u$)

Assign $A, B, C, D$ from the given type of reaction.
$Cr(OH)_3 \downarrow + NH_3 \text{ (excess)} \longrightarrow [Cr(NH_3)_6]^{3+}$

Which among the following is the strongest ligand?

Which from the following is a correct stability order of complexes formed by metal ions if the ligand remains the same?