What is the number of moles of donor atoms in $n$ mole of $NO_2^{-}$?

Which of the following coordination complexes contains a neutral ligand?

Consider the coordination compound,$[Co(NH_3)_6]Cl_3$. In the formation of this complex,the species which acts as the Lewis acid is

In potassium trioxalatoaluminate $(III)$, what are the primary and secondary valency of the central atom respectively?

The total number of ions present in $K_4[Fe(CN)_6]$ is .....

The mass of carbon present in $0.5 \, mol$ of $K_4[Fe(CN)_6]$ is .............. $g$.