Which of the following represents a chelating ligand?

Which of the following ligands possesses only one coordination site?

Addition of excess of $AgNO_3$ to an aqueous solution of $1$ mole of $PdCl_2 \cdot 4 NH_3$ gives $2$ moles of $AgCl$. The conductivity of this solution corresponds to

$A$ solution of potassium ferrocyanide would contain $.......$ ions.

Which of the following is a negatively charged bidentate ligand?

Define the following term: Coordination sphere.