Generally,a group of atoms can function as a ligand if:

Assertion : When $NO$ reacts with $FeSO_4$,a brown coloured complex is formed.
Reason : In the complex,the coordination number of $Fe$ is $6$.

Identify the total number of complexes having bidentate ligands in them from the following list of complexes:
$a$) Tetracyanonickelate$(II)$ ion
$b$) Trioxalatocobaltate$(III)$ ion
$c$) Sodium hexafluoroaluminate$(III)$
$d$) bis(ethylenediamine)dithiocyanatoplatinum$(IV)$

The coordination number of cobalt in the complex $[Co(en)_2Br_2]Cl_2$ is

Potassium ferrocyanide is a

The formula of sodium nitroprusside is