$NH_2-NH_2$ acts as a .......

The equivalents of ethylene diamine $(en)$ required to replace the neutral ligands from the coordination sphere of the trans-complex of $CoCl_{3} \cdot 4NH_{3}$ is ............ (Round off to the Nearest Integer).

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

An excess of $AgNO_3$ is added to $100 \ mL$ of a $0.01 \ M$ solution of dichlorotetraaqua-chromium$(III)$ chloride. The number of moles of $AgCl$ precipitated would be

Which is the correct match for the complex and the number of chelate rings formed?
Complex $-$ No. of Rings

What is a coordination compound?