What is the number of electrons lost by $Cr$ in a complex $[Cr(CO)_6]$?

What is the number of moles of silver chloride precipitated when excess silver nitrate is treated with one mole of pentaamminecarbonatocobalt$(III)$ chloride?

Homoleptic complexes among the following are:
$(A)$ $K_3[Al(C_2O_4)_3]$
$(B)$ $[CoCl_2(en)_2]^{+}$
$(C)$ $K_2[Zn(OH)_4]$

The number of water molecule$(s)$ directly bonded to the metal centre in $CuSO_4 \cdot 5 H_2 O$ is

Which of the following complexes contains only anionic ligands?

$A$ complex compound of $Co^{3+}$ with molecular formula $CoCl_{x} \cdot yNH_3$ gives a total of $3$ ions when dissolved in water. How many $Cl^{-}$ ions satisfy both primary and secondary valencies in this complex?