inorganic - reactions of ions in aqueous solutions Flashcards
when in aqueous solution without any other ions what is the complex called
-metal aqua ion
what are metal aqua ions and what is their shape
-central metal ion
-surronded by six water ligands
-in an octohedral shape
what is a lewis acid
-species that can bond by accepting a lone pair of electrons
what is a lewis base
-species which can bound by donating a lone pair of electrons
how does metal aqua ions act in accordance with lewis acid/base laws
-metal = lewis acid
-water = lewis base
how does acidity change in metal aqua ions
-the higher the charge on the metal in the metal ion the more acidic
-this is because the higher charge density on the oxygen pulls the water more strongly
-this weakens the O-H bond results in more dissociation and pulls electrons to the O away from the H
-another H2O picks up the electrons from the O to form H3O+ - which is effectively H+
-so acidity increases
-water is said to be polarised
what happens if a metal aqua ions reacts with a base
-hydrolysis takes place - the base removes the H+ pushing the equilibrium right - eg OH-, NH3 , CO3^2-
-insoluble neutral complex will form a precipitate
-addition of excess base the insoluble complex may react further - or may dissolve
what 3 reactions con metal aqua ions undergo
-hydrolysis - loss of H+ from the H2O ligands - O-H bond breaks
-substitution - replacement of H2O by other ligands - metal -ligand bond breaks
-redox - metal changes oxidation state - gain or loss of electrons
how do hydrolysis equations of metal aqua ions work
-lower the charge for the products
-produce a (H2O)x(OH)x and produce H+
-take number away from H2O and put in an OH and a water
what is the pH of a solution with a +ve charge
7
what is the pH of a solution with a 2+ charge
6
what is the pH of a solution with a 3+ charge
3
what is the pH of a solution with a 4+ charge
0
what is the reaction of the iron (II) ion with NaOH
-add OH = green solution - green precipitate
[Fe(H2O)5(OH)] + (aq) + 2OH– (aq) → Fe(H2O)4(OH)2 (s) + 2H2O (l)
-excess OH = no vis change
what is the reaction of iron (II) with ammonia
The ammonia behaves in the same way as sodium hydroxide as it is a base and removes protons from the water ligands; the overall reaction with ammonia is:
[Fe(H2O)6] 2+ (aq) + 2NH3 (aq) → Fe(H2O)4(OH)2 (s) + 2NH4+ (aq)
what is the reaction of iron (II) with carbonate ions
With carbonate ions, the iron(II)carbonate precipitates out:
[Fe(H2O)6] 2+ (aq) + CO32- (aq) → FeCO3 (s) + 6H2O (l)
what is the reaction of copper ion and NaOH
-blue solution to blue precipate
[Cu(H2O)5(OH)] + (aq) + 2OH– (aq) → Cu(H2O)4(OH)2 (s) + 2H2O (l)
-excess NaOH = no vis change
what is the reaction of copper solution and ammonia
The ammonia initially behaves in the same way as sodium hydroxide as it is a base and removes protons from the water ligands
[Cu(H2O)6] 2+ (aq) + 2NH3 (aq) → Cu(H2O)4(OH)2 (s) + 2NH4+ (aq)
However, ammonia is a good ligand and in excess ammonia, the ammonia partially substitutes for water creating the deep blue complex ion, dihydroxytetraaminecopper(II)
Cu(H2O)4(OH)2 (s) + 4NH3 (aq) → [Cu(NH3)4(H2O)2 ]2+ (aq) + + 2OH- (aq) + 2H2O (l)
what is the reaction with copper ions and carbonate ions
[Cu(H2O)6] 2+ (aq) + CO32- (aq) → CuCO3 (s) + 6H2O (l)
what is the reaction of alumminium and NaOH
-white ppt formed
[Al(H2O)4(OH)2] + (aq) + 3OH– (aq) → Al(H2O)3(OH)3 (s) + 3H2O (l)
-add excess NaOH
-white ppt dissolves as it can react further
[Al(H2O)3(OH)3] + OH- = [Al(H2O)3(OH)3]- + H2O
what is the reaction of alumminium and ammonia
The ammonia behaves in the same way as sodium hydroxide as it is a base and removes protons from the water ligands; the overall reaction with ammonia is:
[Al(H2O)6] 3+ (aq) + 3NH3 (aq) → Al(H2O)3(OH)3 (s) + 3NH4+ (aq)
what is the reaction bwt aluminum ions and carbonate ions
{In the previous section we saw that +3 ions are acidic in water, so the addition of carbonate ions liberates bubbles of carbon dioxide:
2H3O+ (aq) + CO32- (aq) → CO2 (g) + 3H2O (l)
The reaction between aluminium and water exists in an equilibrium:
[Al(H2O)6] 3+ (aq) + 3H2O (l) ⇌ Al(H2O)3(OH)3 (s) + 3H3O+ (aq) }
Removal of the hydronium ions by carbonate ions pushes the equilibrium to the right and precipitates out the hydrated aluminium hydroxide
The overall equation can therefore shown as:
2[Al(H2O)6]3+ + 3CO32− (aq) → 2Al(H2O)3(OH)3 (s) + 3CO2 (g) + 3H2O (l)
what is the reaction of iron (III) and NaOH
-green solution to red/brown ppt
-[Fe(H2O)4(OH)2] 3+ (aq) + OH– (aq) → Fe(H2O)3(OH)3 (s) + H2O (l)
-add excess - no vis change
what is the reaction of iron (III) and ammonia
The ammonia behaves in the same way as sodium hydroxide as it is a base and removes protons from the water ligands; the overall reaction with ammonia is:
[Fe(H2O)6] 3+ (aq) + 3NH3 (aq) → Fe(H2O)3(OH)3 (s) + 3NH4+ (aq)
what is the reaction of iron (III) and carbonate ions
the acidity of iron(III) ions removes the carbonate ion and produces bubbles of carbon dioxide, while the iron(III) precipitates out as the hydroxide
The overall equation can therefore shown as:
2[Fe(H2O)6]3+ (aq) + 3CO32− (aq) → 2Fe(H2O)3(OH)3 (s) + 3CO2 (g) + 3H2O (l
what happens when u add excess H+ to each of the solutions
-dissolves the precipitate
what is the colour of the [Cu(H2O)6]2+ ion
blue
what is the colour of the [Co(H2O)6]2+
pink
what is the colour of the [Fe(H2O)6]2+
green
what is the colour of the [V(H2O)6]2+
green
what is the colour of the [Cr(H2O)6]3+
violet
what is the colour of the [Fe(H2O)6]3+
pale violet
what is the colour of the [Al(H2O)6]3+
colourless
What is Ligand substitution
When one ligand in a complex is replaced by another
How does the coordination number of a metal ion ligand change
If the ligands are of different sizes
If larger there will be a decrease in coordination number
Does the coordination number change if the ligands are the same size
No stays the same
Eg ammonia and water liando are of similar size
What is the chelate effect
Substitution of ligands that can form more coordinate bonds than the previous ligand
How does entropy and enthalpy and Gibbs’s free energy apply to the chelate effect
Increase in entropy - increase in the number of particles - more disorder
Negligible change in the enthalpy
Therefore gibbs free energy is more negative - so the reaction is more feasible when there is a larger number of ligands
What is a chelate
-complex ions with polydentate ligands - useful in removing d-block metal ions from solution
What are chelating agents
Ligands that form more than 1 coordinate bond
-good at binding to the metal ion and harder to be substituted
What is the most stable ligand and why
EDTA4- as it forms 6 coordinate bonds from one ligand - therefore is harder to remove
What are the next stable ligands after EDTA4-
C2O4-
H2O
Cl-
