Colours Flashcards
What is a hexaaqua ion?
Transition metal ions in aqueous solution form ionic complexes with 6 coordinately bonded water molecules surrounding a central metal ion. The complex overall has a charge
What is the colour of [Fe(H20)6]2+?
Green solution
What happens if [Fe(H20)6]2+ is left in air?
Oxidised (to Fe3+) - yellow solution
What happens to [Fe(H20)6]2+ when OH- is added?
Acid-base reaction
[Fe(H20)4(OH)2] PRECIPITATE FORMS
This is a green precipitate
What happens to [Fe(H20)6]2+ in a reaction with ammonia?
[Fe(H20)4(OH)2] PRECIPITATE FORMS
This is a green precipitate
What happens to [Fe(H20)6]2+ in a reaction with carbonate?
FeCO3
This is a green precipitate
What is the colour of [Cu(H20)6]2+?
Blue solution
What happens to [Cu(H20)6]2+ when OH- is added?
[Cu(H20)4(OH)2] ppt forms
This is a blue precipitate
What happens to [Cu(H20)6]2+ when NH3 is added (including in excess)?
[Cu(H20)4(OH)2] ppt forms initially: blue precipitate (acid-based)
Excess ammonia leads to ligand substitution: [Cu(NH3)4(H2O)2] ppt forms
What happens to [Cu(H20)6]2+ in a reaction with carbonate?
CuCO3 ppt - blue-green precipitate
What is the colour of [CoH20)6]2+?
Pink solution
Under what conditions can cobalt be oxidised?
Under alkaline conditions
What happens to [Co(H20)6]2+ when OH- is added? And what happens if this is left standing in air?
[Co(H20)4(OH)2] ppt forms initially: blue-green precipitate (acid-base)
On standing it is a bit weird so a pink solution can form which then turns to a brown precipitate (in which you have a cobalt (III) hydroxide: Co(H20)3(OH)3)
What is the difference between a complex ion and a precipitate?
Precipitates are uncharged! If the transition metal complex is uncharged it is a precipitate
What happens to [Co(H20)6]2+ when ammonia is added? What happens when ammonia is in excess? And what happens if this is left standing in air?
[Co(H20)4(OH)2] ppt forms initially: blue-green precipitate (acid-base)
[Co(NH3)6]2+ (this really is awesome … COMPLETE SUBSTITUTION IN EXCESS!)
Again in air a bit weird … but can be oxidised to a dark brown solution (again reflects the fact that cobalt (III) is in the solution
What happens to cobalt when carbonate is added?
CoCO3 forms which is a purple precipitate
What is the colour of [Cr(H20)6]3+?
Pale green solution
What is the colour of [Fe(H20)6]3+?
Yellow solution
What is the colour of [Al(H20)6]3+?
Colourless
What happens to [Cr(H20)6]3+ when OH- is added? What happens when OH- is in excess?
Grey green precipitate: Cr(OH)3(H2O)3 (acid-base)
Dark green solution: [Cr(OH)6]3- (ligand substitution when in excess - one of the only ones that do this with hydroxide)
What happens to [Fe(H20)6]3+ when OH- is added? What happens when OH- is in excess?
Red-brown precipitate: Fe(OH)3(H2O)3 (acid-base)
IN EXCESS: Erm … nothing new!
What happens to [Al(H20)6]3+ when OH- is added? What happens when OH- is in excess?
White precipitate: Al(OH)3(H2O)3 (acid-base)
Colourless solution: [Al(OH)4(H2O)2]- (ligand substitution when in excess - one of the only ones that do this with hydroxide)
What happens to [Cr(H20)6]3+ when NH3 is added? What happens when NH3 is in excess?
Grey green precipitate: Cr(OH)3(H2O)3 (acid-base)
Violet solution: [Cr(NH3)6]3+ (ligand substitution)
