In the complex ion $[Co(NH_3)_6]^{3+}$,the $NH_3$ molecules are linked to the metal atom by .......

Define the following terms:
$1$. Ligands
$2$. Coordination number

$A$ 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?

Which of the following is a neutral complex?

The number of ions produced when one molecule of $FeSO_4 \cdot (NH_4)_2SO_4 \cdot 6H_2O$ is dissolved in water is ...............

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