The coordination number of $Fe(II)$ in oxyhemoglobin is ..........

Which of the following ligands is neutral?

The bonds in ${K_4[Fe(CN)_6]}$ are

The sum of the oxidation state (magnitude) and the coordination number of cobalt in $Na[Co(bpy)Cl_4]$ is $.......$ (Given $bpy = 2,2'-bipyridine$)

Which one of the following forms a complex with an excess of $CN^{-}$ (cyanide) having a coordination number of two?

What is the number of moles of ionisable $Cl^{-}$ ions in a coordination complex if it forms $2 \ moles$ of $AgCl$ when treated with silver nitrate solution in excess?