[Cu(H2O)6]2+ is typically blue due to the d-d transitions of the copper ion in an octahedral field.

In the complex ion [Co(NH3)6]Cl3, the central metal ion Co is surrounded by 6 ammonia (NH3) ligands, which gives it a coordination number of 6.

In the complex [Co(NH3)5Cl]Cl2, cobalt is surrounded by five ammonia ligands and one chloride ligand, giving it a coordination number of 6.

The coordination number is determined by the number of ligands attached to the central metal ion. Here, Co is surrounded by 6 NH3 ligands.

The complex formed is [Fe(SCN)3] as iron(III) can bond with three thiocyanate ions.

The complex [Ag(NH3)2]+ has a linear geometry due to the presence of two ligands around the silver ion.

In [Ni(CO)4], the nickel atom undergoes sp3 hybridization to accommodate four CO ligands.

In [Cr(NH3)6]3+, the hybridization is d2sp3 due to the octahedral arrangement of six ligands.

In K2Cr2O7, the total charge from potassium (K) is +2, and oxygen (O) contributes -14. Let the oxidation state of Cr be x. The equation is 2x - 14 + 2 = 0, solving gives x = +6.

[CoCl2(NH3)4]+ can exhibit geometrical isomerism due to the different arrangements of ligands around the cobalt ion.

[Fe(H2O)6]3+ has unpaired electrons, making it paramagnetic, while the others have all paired electrons.

EDTA can form multiple bonds with a metal ion, making it a bidentate ligand as it can attach at two sites.

CN- is a strong field ligand that causes a large splitting of d-orbitals, leading to low-spin complexes.

Coordination compounds can exhibit optical isomerism due to the arrangement of ligands around the central metal ion.

The complex [Fe(CN)6]3- is a low-spin complex due to the strong field nature of CN- ligands, resulting in paired electrons.