Metal Aqua Ions

What do a Lewis Acid and Lewis Base form?

A coordinate bond

What is an example of Lewis Acids and Bases?

A ligand is a Lewis base- Donates a lone pair of electrons- to a central metal ion- which is a Lewis acid

What is a Lewis Acid? What is a Lewis Base?

Accepts a pair of electrons Donates a pair of electrons

What affects acidity in hydrolysis of metal aqua ions? Which ions have a higher charge/size ratio? What does this mean

Acid strength generally increases as the size of the ion decreases and the charge increases Al3+, Cr3+, Fe3+ in comparison to Fe2+, Co2+, Cu2+ They have greater polarizing power and attract more strongly the electron density from the oxygen in the aqua ligands so the O-H bond becomes weakeer

Which two metal hydroxides are amphoteric? What does this mean

Aluminium hydroxide [Al(H2O)3(OH)3] Chromium hydroxide [Cr(H2O)3(OH)3] They react with excess acid and excess base

[M(H2O)6]3+ Complexes and Colours (and the exception- why it forms a hexaaqua complex)

Aluminium- Forms a hexaaqua complex because it has a high charge density [Al(H2O)6]3+ Colourless Chromium- [Cr(H2O)6]3+ Ruby Iron- [Fe(H2O)6]3+ Pale Violet

[M(H2O)6]2+ Complexes and Colours

Copper- [Cu(H2O)6]2+ Blue Cobalt- [Co(H2O)6]2+ Pink Iron- [Fe(H2O)6]2+ Pale Green

What name and shape and coordination number do metal- aqua ions form?

Hexaaqua complexes Octahedral 6

When aluminium forms a hexaaquaaluminium (III) complex, what pH is the resulting solution and why

It is pH3, acidic, because the complex reacts with water further in a hydrolysis reaction

Which metal ions are the most polarizing What happens as a result

Small ions with a high charge density- a high charge/ size ratio The ions can polarize their aqua ligands and weaken the O-H bond and then water acts as a bronsted lowry base and removes a H+ ion from the aqua ligand, forming H3O+

What two types of reaction do metal aqua ions undergo and what does that depend on

Substitution reaction- if the coordinate bond between the ligand and metal ion is broken it is replaced by a different ligand Hydrolysis reaction- if the O-H bond is broken in an aqua ligand a hydrogen ion is released

Why does a metal- aqua ion form?

Transition metal ions, such as Fe2+ and Fe3+, have a high charge density which attracts the lone pair on the O from a water molecule. A lone pair is donated to the metal ion forming a covalent bond.

What happens when aluminium hydroxide and chromium hydroxide react with excess acid

[Al(H2O)3(OH)3] + H3O+ -> [Al(H2O)6]3+ + 3H2O White -> colourless [Cr(H2O)3(OH)3] + H3O+ -> [Al(H2O)6]3+ + 3H2O Grey green -> ruby

What happens when aluminium hydroxide and chromium hydroxide react with excess base?

[Al(H2O)3(OH)3] + OH- -> [Al(OH)4]- + 3H2O White -> colourless [Cr(H2O)3(OH)3] + OH- -> [Cr(OH)4]- + 3H2O Grey green -> dark green

M3+ metal aqua ions and ammonia Aluminium (III) Chromium (III) Iron (III)

[Al(H2O)3]3+ + 3NH3 -> [Al(H2O)3(OH)3] + 3NH4+ Colourless -> White [Cr(H2O)6]3+ + 3NH3 -> [Cr(H2O)3(OH)3] + 3NH4+ Ruby -> Grey green [Fe(H2O)6]3+ +3NH3 -> [Fe(H2O)3(OH)3] + 3NH4+ Violet -> Brown

M3+ metal aqua ions and carbonate ion Aluminium (III) Chromium (III) Iron (III)

[Al(H2O)6]3+ + 3CO3 2- -> [Al(H2O)3(OH)3] + 3H2O + 3CO2 Colourless -> White [Cr(H2O)6]3+ + 3CO3 2- -> [Cr(H2O)3(OH)3] + 3H2O + 3CO2 Ruby -> Grey green [Fe(H2O)6]3+ + 3CO3 2- -> [Fe(H2O)3(OH)3] + 3H2O + 3CO2 Violet -> Brown

M3+ metal aqua ions and hydroxide ions Aluminium (III) + colour change What happens when the aluminium precipitate redissolves

[Al(H2O)6]3+ + 3OH- -> [Al(H2O)3(OH)3] +3H2O Colourless -> White Redissolves to form tetrahydroxoaluminate [Al(OH)4]- [Cr(H2O)6]3+ + 3OH- -> [Cr(H2O)3(OH)3] + 3H2O Ruby -> Grey green

What is the hydrolysis reaction of hexaaquaaluminium (III) with water Which part acts as a Bronsted Lowry acid or base Where does the position of the equilibrium lie

[Al(H2O)6]3+ + H2O -> [Al(H2O)5(OH)] 2+ + H3O+ Pentaaquahydroxoaluminium (II) acts as the acid because it donates a H+ to water To the left which makes it weakly acidic

M3+ metal aqua ions and hydroxide ions Chromium (III) + colour change What happens when the chromium precipitate redissolves

[Cr(H2O)6]3+ + 3OH- -> [Cr(H2O)3(OH)3] + 3H2O Ruby -> Grey green Redissolves to form hexahydroxochromate (III) complex [Cr(H2O)3(OH)3] + 3OH- -> [Cr(OH)]3- + 3H2O Grey green -> Dark green

Hydrolysis reactions from the hexaaqua complexes Chromium (III) Iron (III) Copper (II) Cobalt (II) Iron (II)

[Cr(H2O)6]3+ + H2O -> [Cr(H2O)5(OH)]2+ + H3O+ [Fe(H2O)6]3+ + H2O -> [Fe(H2O)5(OH)]2+ + H3O+ [Cu(H2O)6]3+ + H2O -> [Cu(H2O)5(OH)]+ + H3O+ [Co(H2O)6]3+ + H2O -> [Cu(H2O)5(OH)]+ + H3O+ [Fe(H2O)6]3+ +H2O -> [Fe(H2O)5(OH)]+ + H3O+

M2+ metal aqua ions and ammonia Copper (II) Iron (II) Cobalt (II)

[Cu(H2O)6]2+ + 2NH3 -> [Cu(H2O)4(OH)2] + 2NH4+ Blue -> Blue [Fe(H2O)6]2+ + 2NH3 -> [Fe(H2O)4(OH)2] + 2NH4+ Pale green -> Green [Co(H2O)6]2+ + 2NH3 -> [Co(H2O)4(OH)2] + 2NH4+ Pink -> Blue green

M2+ metal aqua ions and hydroxide ions Copper (II) + colour change Cobalt (II) + colour change Iron (II) + colour change

[Cu(H2O)6]2+ + 2OH- -> [M(H2O)4(OH)2] + 2H2O Blue -> blue [Co(H2O)6]2+ + 2OH- -> [M(H2O)4(OH)2] + 2H2O Pink -> Blue green [Fe(H2O)6]2+ + 2OH- -> [M(H2O)4(OH)2] + 2H2O Pale green -> Green

M2+ metal aqua ions and carbonate ion Copper (II) Iron (II) Cobalt (II)

[Cu(H2O)6]2+ + CO3 2- -> CuCO3 + 6H2O Blue -> Green blue [Fe(H2O)6]2+ + CO3 2- -> FeCO3 + 6H2O Pale green -> Green [Co(H2O)6]2+ + CO3 2- -> CoCO3 + 6H2O Pink -> Pink

M3+ metal aqua ions and hydroxide ions Iron (III) + colour change

[Fe(H2O)6]3+ + 3OH- -> [Cr(H2O)3(OH)3] + 3H2O Violet -> Brown

What does an aqueous solution of M2+ metalhexaaqua ions contain What happens when hydroxide ions are added What happens to the equilibrium What forms as a result Overall equation

[M(H2O)6]2+ and a small proportion of [M(H2O)5(OH)]+ The hydroxide ions act as a base and react with the H3O+ The equilibrium moves to the right An insoluble metal hydroxide precipitate forms [M(H2O)6]2+ + 2OH- -> [M(H2O)4(OH)2] (s) + 2H2O

What does an aqueous solution of M3+ metal hexaaqua ions contain What happens when hydroxide ions are added What happens to the equilibirum Overall equation

[M(H2O)6]3+ and a small proportion of [M(H2O)5(OH)]+ The hydroxide ions act as a base and react with the H3O+ The equilibrium moves to the right and further reaction occurs again moving it more to the right [M(H2O)6]3+ + 3OH- -> [M(H2O)3(OH)3] + 3H2O