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!)
Which complex ion is amphoteric? Why?
[Cr(H2O)3(OH)3]
Can react with both acids and alkali
When reacted with acids, will form [Cr(H2O)6]3+
When reacted with alkali, will form [Cr(OH)6]3-
What colour is [CuCl4]2- ?
Yellow / green
Dilute aqueous ammonia is added, drop by drop, to an aqueous solution of copper(II) sulfate until the aqueous ammonia is in excess.
Describe what you would see during this experiment. (2 marks)
Write the equation for the exaction with excess aqueous ammonia. (2 marks)
Blue precipitate forms
And redissolved into DEEP blue SOLUTION
[Cu(H2O)6]2+ + 4NH3 -> [Cu(NH3)4(H2O)2]2+ + 4H2O
