What is the total number of ions in the aqueous solution of ferric hexacyanoferrate $(II)$?

Define the following term: Coordination sphere.

What type of ligand is the oxalate ion?

Trioxalato aluminate $(III)$ and tetrafluoro-borate $(III)$ ions are :

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 of the following coordination complexes contains the ligand $en$?