What is the total number of donor atoms present in the Tetracyanonickelate$(II)$ ion?

Potassium ferrocyanide is a

In the complex $[E(en)_2(C_2O_4)]NO_2$,the oxidation state and coordination number of the element $'E'$ are respectively (where $(en)$ is ethylenediamine):

What is the total number of donor atoms in $[Co(H_2O)(NH_3)_5]I_3$?

Which of the following is a double salt?

One mole of the coordination compound $Co(NH_3)_5Cl_3$ gives $3$ moles of ions upon dissolution in water. Furthermore,one mole of this complex reacts with $2$ moles of $AgNO_3$ solution to produce $2$ moles of $AgCl(s)$. The structure of the complex is: