Reactions Of Inorganic Complexes Flashcards
Colour of [Cu(H2O)6]2+ as aqueous ion
Blue solution
Colour of [Co(H2O)6]2+
Pink
Colour of [Fe(H2O)6]2+
Green
Colour of [V(H2O)6]3+
Green
Colour of [V(H2O)6]2+
Violet
Colour of [Cr(H2O)6]3+
Violet
Usually appears as deep purple rather than violet in solution.
Note: Colour of Cr3+ is green in reactions due to substitution of other negative ions
Colour of [Fe(H2O)6]3+
Pale violet
Usually appear yellow/orange rather than violet in solution due to [Fe(H2O)5(OH)]2+ forming by hydrolysis
Colour of [Al(H2O)6]3+
Colour less
Aluminium is included but only one that isn’t a transition metal
Define hydrolysis
A reaction with a water molecule that breaks large molecules into smaller ones.
Why do hexaaqua complexes undergo hydrolysis
due to the polarising nature of the central transition metal ion.
The transition metal pulls electron density towards the metal, weakening the existing O-H bonds within the water ligands.
Give an equation to show the acid base reaction of
H3O+ and OH
H3O+ + OH- → 2H2O
Predict, and justify, how the addition of sodium hydroxide solution will effect the above equilibrium.
[Cu(H2O)6]2+(aq) + H2O(l) ⇌ [Cu(H2O)5(OH)]+(aq) + H3O+(aq)
The hydroxide ion will react with the hydroxonium ion, reducing the concentration of hydroxonium ion in the system. Equilibrium of the top reaction will shift to the right to increase the concentration of hydroxonium ion, opposing this change.
Give the overall equation for the reaction between hexaquacopper(II) solution and sodium hydroxide solution.
And colour
[Cu(H2O)6]2+(aq) + 2OH- → Cu(H2O)4(OH)2 + 2H2O(l)
Blue ppt
Give equations of [Fe(H2O)6]2+ + NaOH(aq) drop wise and in excess
Both colours
Dropwise: [Fe(H2O)6]2+ + 2OH- → Fe(H2O)4(OH)2 + 2H2O (hydrolysis)
Green ppt but goes brown on standing air
Excess: no further reaction but darkens in time on oxidation to [Fe(H2O)3(OH)3] (s)
No further change
Give equations for [Cu(H2O)6]2+ + NaOH(aq) drop wise and in excess
And colours
Dropwise: [Cu(H2O)6]2+ + 2OH- → [Cu(H2O)4(OH)2] + 2H2O (hydrolysis)
Blue ppt
Excess: no further reaction
No change
Give equations for [Fe(H2O)6]3+ + NaOH(aq) drop wise and in excess
Dropwise: [Fe(H2O)6]3+ + 3OH- → [Fe(H2O)3(OH)3] + 3H2O (hydrolysis)
Brown ppt
Excess: no further reaction
No change
Give equations for [Al(H2O)6]3+ + NaOH(aq) drop wise and in excess
Dropwise: [Al(H2O)6]3+ + 3OH- → [Al(H2O)3(OH)3] + 3H2O (hydrolysis)
Colourless
Excess: [Al(H2O)3(OH)3] + OH- → [Al(H2O)2(OH)4]- + H2O (hydrolysis)
White ppt
General rules for aqua ions and OH-(aq)
• Dropwise – precipitate of neutral metal(II) hydroxide or metal(III) hydroxide forms
• Excess - [Al(H2O)3(OH)3] undergoes further hydrolysis to [Al(H2O)2(OH)4]- and so ‘re-dissolves’
Amphoteric meaning
Characteristics of an acid and base
[Fe(H2O)6]2+ + NH3(aq)
Dropwise and in excess
Colours
Dropwise: [Fe(H2O)6]2+ + 2NH3 → [Fe(H2O)4(OH)2] (s)+ 2NH4+ (hydrolysis)
Green pot and goes brown on standing air
Excess: no further reaction but darkens in time on oxidation to [Fe(H2O)3(OH)3]
[Cu(H2O)6]2+ + NH3(aq)
Drop wise
In excess
And colour
Dropwise: [Cu(H2O)6]2+ + 2NH3 → [Cu(H2O)4(OH)2] (s)+ 2NH4+ (hydrolysis)
Blue ppt
Excess: [Cu(H2O)4(OH)2] + 4NH3 → [Cu(H2O)2(NH3)4]2+ + 2H2O + 2OH- (substitution
Deep blue solution
[Fe(H2O)6]3+ + NH3(aq)
Dropwise
In excess
Colours
Dropwise: [Fe(H2O)6]3+ + 3NH3 → [Fe(H2O)3(OH)3] (s)+ 3NH4+ (hydrolysis)
Brown ppt
Excess: no further reaction
[Al(H2O)6]3+ + NH3(aq)
Drop wise
In excess
Dropwise: [Al(H2O)6]3+ + 3NH3 → [Al(H2O)3(OH)3] (s)+ 3NH4+ (hydrolysis)
White ppt
Excess: no further reaction
General rules for metal aqua ions and NH3(aq)
• Dropwise – precipitate of metal(II) hydroxide or metal(III) hydroxide forms
• Excess – [Cu(H2O)4(OH)2] undergoes ligand substitution to give [Cu(H2O)2(NH3)4]2+
[Fe(H2O)6]2+ + CO32-(aq)
Colour
[Fe(H2O)6]2+ + CO32- → FeCO3 (s)+ 6H2O (precipitation)
Green ppt
[Cu(H2O)6]2+ + CO32-(aq)
Colour
[Cu(H2O)6]2+ + CO32- → CuCO3 (s)+ 6H2O (precipitation)
Blue - green ppt
[Fe(H2O)6]3+ + CO32-(aq)
2 [Fe(H2O)6]3+ + 3CO32- → 2[Fe(H2O)3(OH)3] (s)+ 3H2O + 3CO2 (hydrolysis)
brown ppt
(ppt may look orange-brown)
and CO2 gas evolved
[Al(H2O)6]3+ + CO32-(aq)
Colour
2[Al(H2O)6]3+ + 3CO32- → 2[Al(H2O)3(OH)3] (s)+ 3H2O + 3CO2 (hydrolysis)
white ppt
and CO2 gas evolved
General rules of metal aqua ions + CO3^2-(aq)
• [M(H2O)6]2+ forms MCO3 as precipitate (it is not acidic enough to release CO2 from Na2CO3)
• [M(H2O)6]3+ is more acidic and undergoes hydrolysis to form [M(H2O)3(OH)3] as a precipitate and gentle fizzing as CO2 is formed
Colour of [Cu(H2O)6]2+ with NaOH
Blue ppt
You
Better
Get
Vanadium
Yellow [VO2(H2O)4]+
Blue [VO(H2O)5]2+
Green [V(H2O)6]3+
Violet [V(H2O)6]2+
[V(H2O)6]2+ oxidation state
V(II)
[V(H2O)6]3+ oxidation state
V(III)
VO(H2O)5]2+ oxidation state
V(IV)
[VO2(H2O)4]+ oxidation state
V(V)
[Co(H2O)6]2+ + NH3(aq)
Dropwise
In excess
Overall
And colour change
Dropwise: [Co(H2O)6]2+ + 2NH3 → [Co(H2O)4(OH)2] + 2NH4+ (hydrolysis) pink to blue ppt
Excess: [Co(H2O)4(OH)2] + 6NH3 → [Co(NH3)6]2+ + 4H2O + 2OH- (substitution) blue to pale brown
Overall: [Co(H2O)6]2+ + 6NH3 → [Co(NH3)6]2+ + 6H2O (substitution) pink to pale brown
[Cu(H2O)6]2+ + NH3(aq)
Dropwise and in excess
Overall
Dropwise: [Cu(H2O)6]2+ + 2NH3 → [Cu(H2O)4(OH)2] + 2NH4+ (hydrolysis) blue to blue ppt
Excess: [Cu(H2O)4(OH)2] + 4NH3 → [Cu(H2O)2(NH3)4]2+ + 2H2O + 2OH- (substitution) deep blue solution
Overall: [Cu(H2O)6]2+ + 4NH3 → [Cu(H2O)2(NH3)4]2+ + 4H2O (substitution)
How many Cl- fit around M^n+
4
[Co(H2O)6]2+ + conc HCl
[Co(H2O)6]2+ + 4Cl- → [CoCl4]2- + 6H2O (substitution)
Pink to blue
[Cu(H2O)6]2+ + conc HCl
[Cu(H2O)6]2+ + 4Cl- → [CuCl4]2- + 6H2O (substitution)
Blue to green
