Complex Ion + TM Colours Flashcards
What is the colour of copper(II) ions in solution?
Blue
What colour is the complex ion [Fe(H2O)6]2+?
Green
What is the colour of the complex ion [Co(H2O)6]2+?
pink
What is the color of the complex ion [Cr(H2O)6]3+?
Green
What colour is the complex ion [MnO4]–?
Purple
Which ion typically gives a green color in solution?
Fe2+
or
Cr3+
What colour is Fe3+?
yellow
What is the color of [CoCl4]2- complex?
Blue
Multiple Choice: Which of the following is a blue transition metal complex? A) [Cu(H2O)6]2+ B) [Fe(H2O)6]3+ C) [Co(H2O)6]2+ D) [MnO4]–
A) [Cu(H2O)6]2+
What color does the complex ion [Co(NH3)6]3+ exhibit?
Yellow/brown
What colour would Fe3+ turn from and to, if left in air?
Yellow to brown
As it’s oxidised by air
[Fe(H2O)6]2+ + 2OH- ->
What reaction is it?
[Fe(H2O)4(OH)2] (s) + 2H2O
Deprotonation
[Co(H2O)6]2+ + 2OH- ->
[Co(H2O)4(OH)2] + 2H2O
deprotonation
Pale pink to blue
[Cu(H2O)6]2+ + xNH3 ->
give products of 1. some ammonia added and 2. excess
and colour change
from blue to
1. Blue ppt - deprotonation
[Cu(H2O)4(OH)2] (s) + 2NH4+
2. Deep blue solution - ligand exchange
[Cu(NH3)4(H2O)2] + 2H2O + 2OH-
[Co(H2O)6]2+ + xNH3 ->
give products of 1. some ammonia added and 2. excess
and colour change
from pale pink to
1. blue ppt
[Co(H2O)4(OH)2] + 2NH4+
2. brown solution
[Co(NH3)6]2+ (aq) + 4H2O +2OH-
What colour is Fe3+?
Yellow solution
[Fe(H2O)6]3+ + 3OH- ->
or
[Fe(H2O)6]3+ + 3NH3 ->
[Fe(H2O)3(OH)3] (s) + 3H2O
both yellow to orange
[Fe(H2O)3(OH)3] (s) + 3NH4+
What colour is [Cr(NH3)6]3+?
violet solution
[Cr(H2O)6]3+ + 3OH- ->
and excess OH
green solution to green ppt
[Cr(H2O)3(OH)3] (s) + 3H2O
excess makes green solution again
[Cr(OH)6]3- + 3H2O
[Cr(H2O)6]3+ + NH3 ->
1. add some
2. add excess
what are the colour changes and products
- green ppt
[Cr(H2O)3(OH)3] (s) + 3NH4+ - violet solution
[Cr(NH3)6]3+ (aq) + 3H2O + 3OH-
What reaction is the reaction
[Fe(H2O)6]2+ + H2O -> [Fe(H2O)5(OH)]+ + H3O+
Acid base behaviour
As involves gaining and losing e-s
Why do Transition metals have colours?
- the five d orbitals have different energy levels
- gap in energy between d orbitals correspond to the energy of UV/visible light
- e-s absorb different wavelengths to promote e-s
- so reflects different unabsorbed wavelengths (of diff colours!)
