Schweitzer's reagent,used for dissolving cellulose in the manufacture of artificial silk,is

Dimethyl glyoxime gives a red precipitate with $Ni^{2+}$,which is used for its detection. To get this precipitate readily,the best $pH$ range is

Assertion: $AgCl$ dissolves in $NH_4OH$ solution.
Reason: Due to formation of a complex.

Which one of the following gives Prussian blue colour?

Sodium thiosulphate $(Na_2S_2O_3 \cdot 5H_2O)$ is used in photography to

If a didentate ligand ethane-$1, 2$-diamine is progressively added in the molar ratio $en : Ni :: 1: 1, 2: 1, 3: 1$ to $[Ni(H_2O)_6]^{2+}$ aqueous solution,the following coordination entities are formed:
$I$. $[Ni(H_2O)_4en]^{2+}_{(aq)} -$ pale blue
$II$. $[Ni(H_2O)_2(en)_2]^{2+}_{(aq)} -$ blue/purple
$III$. $[Ni(en)_3]^{2+}_{(aq)} -$ violet
The wavelengths in $nm$ of light absorbed in the case of $I$ and $III$ are respectively: