What is the correct systematic name for the compound [Co(NH₃)₄(OH₂)₂]Cl₃?

Out of the following complexes [Fe(OH₂)₆]Cl₂ and [Fe(OH₂)₆]Cl_3, which one is more acidic and why?

a)  [Fe(OH₂)₆]Cl₂, because Fe²⁺ has a lower charge density and polarises water molecules more strongly. 

b) [Fe(OH₂)₆]Cl₂, because Fe²⁺ has a higher charge density and releases protons easily. 

c)  [Fe(OH₂)₆]Cl₃, because Fe³⁺ has a higher charge density and polarises water molecules more strongly, weakening the O–H bond. 

d)  [Fe(OH₂)₆]Cl₃, because Fe³⁺ has a lower charge density and thus makes the solution acidic.

How many step-wise equilibrium processes are there for the displacement of six aqua ligands by three ethylenediamine (en) ligands around an octahedral metal ion? 

The overall equation is:

[M(OH_2​)₆​]ⁿ⁺+   3 en  ⟶    [M(en)_3​]ⁿ⁺ +  6 H_2​O

Which of the following molecules could NOT act as a ligand?

Indicate which of the following reagents have a MEDIUM risk.