Transition metals Cobalt reactions

Question 1

[Co(H2O)6]2+ +2OH- aqueous NaOH
Colour change?
Acid base or ligand substitution?

Answer 1

[Co(OH)2(H2O)4] +2H2O
Pale pink solution to blue precipitate
Acid base reaction- 2 H2O ligands deprotonated and converted into 2OH- ligands
2OH- added accept H donated from deprotonated ligand and is converted to H2O, acting as a base.

Question 2

[Co(H2O)6]2+ +2NH3 aqueous ammonia
Colour change?
Acid base or ligand substitution?

Answer 2

[Co(OH)2(H2O)4] +2NH4+
Pale pink solution to blue precipitate
Acid base reaction- 2 H2O ligands deprotonated and converted to 2 OH- ligands
2 NH3 added accept donated H, acting as bases

Question 3

[Co(OH)2(H2O)4] + 6NH3 excess ammonia
Colour change?
Acid base or ligand substitution?

Answer 3

[Co(NH3)6]2+ +2OH- +4H2O
Blue precipitate to yellow solution
Ligand exchange

Question 4

When [Co(NH3)6]2+ is left to stand what reaction occurs?

Colour change?

Answer 4

[Co(NH3)6]2+ to [Co(NH3)6]3+
Oxidation reaction
From yellow solution to brown solution

Question 5

[Co(H2O)6]2+ 4Cl-
Colour change?
Acid base or ligand substitution?
Example of?

Answer 5

[CoCl4]2-+ 6H2O
Pale pink solution to blue solution
Ligand substitution
Example of change in coordination number from 6 to 4, and so a change in shape from octahedral to tetrahedral