The substitution reaction between [Fe H2O 6]2+ and NH3 to form [Fe NH3 6]2+ can be explained using coordination chemistry principles. The reaction involves the replacement of water molecules H2O coordinated to the central iron Fe atom with ammonia molecules NH3 . The mechanism for this reaction can be described in the following steps:1. Formation of the initial complex: The hexaaqua complex, [Fe H2O 6]2+, consists of a central Fe2+ ion surrounded by six water molecules acting as ligands. These water molecules are coordinated to the Fe2+ ion through their oxygen atoms, forming coordinate covalent bonds.2. Ligand exchange: Ammonia NH3 is a stronger ligand than water H2O due to its higher electron-donating ability. As a result, NH3 molecules can replace the H2O molecules in the coordination sphere of the Fe2+ ion. This process is called ligand exchange or ligand substitution.3. Stepwise substitution: The ligand exchange process occurs stepwise, with one NH3 molecule replacing one H2O molecule at a time. The substitution can be described by the following series of equilibrium reactions:[Fe H2O 6]2+ + NH3 [Fe H2O 5 NH3 ]2+ + H2O[Fe H2O 5 NH3 ]2+ + NH3 [Fe H2O 4 NH3 2]2+ + H2O[Fe H2O 4 NH3 2]2+ + NH3 [Fe H2O 3 NH3 3]2+ + H2O[Fe H2O 3 NH3 3]2+ + NH3 [Fe H2O 2 NH3 4]2+ + H2O[Fe H2O 2 NH3 4]2+ + NH3 [Fe H2O NH3 5]2+ + H2O[Fe H2O NH3 5]2+ + NH3 [Fe NH3 6]2+ + H2O4. Completion of the reaction: As the reaction progresses, more and more water molecules are replaced by ammonia molecules. Eventually, all six water molecules are replaced by ammonia molecules, resulting in the formation of the final product, [Fe NH3 6]2+.In summary, the substitution reaction between [Fe H2O 6]2+ and NH3 to form [Fe NH3 6]2+ involves a stepwise ligand exchange process, in which ammonia molecules replace water molecules in the coordination sphere of the Fe2+ ion due to their stronger electron-donating ability.