Post on 27-Dec-2015
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Metal aqua ions
Hydrolysis
Metal aqua ions + OH-
Metal aqua ions + NH3
Metal aqua ions + CO32-
Substitution by Cl-
Substitution by NH3
Summary 1
Chelate effect
Redox
Summary 2
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METAL AQUA IONS
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METAL AQUA IONS
e.g.[Cu(H2O)6]2+
OH2
Cu
OH2
H2O OH2
H2O OH2
2+
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METAL AQUA IONS
complex colour
[Cu(H2O)6]2+ blue
[Co(H2O)6]2+ pink
[Fe(H2O)6]2+ green
[V(H2O)6]2+ green
[Cr(H2O)6]3+ violet*
[Fe(H2O)6]3+ pale violet**
[Al(H2O)6]3+ colourless
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REACTIONS
1) Hydrolysis O-H bond in H2O ligand breaks
2) Substitution M-ligand bond breaks
3) Redox change in oxidation state of M
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HYDROLYSIS
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HYDROLYSIS OF Mn+(aq)
3+
MO O
O O
O
O H
H
H
H
H H
H
H
H
H
H H
MO O
O O
O
O H
H
H
H
H H
H
H
H
H
H
2+
+ H+
2+2+
HYDROLYSIS OF Mn+(aq)
MO O
O O
O
O H
H
H
H
H H
H
H
H
H
H H
n+
M3+ more acidic due to:
M3+ smaller and greater charge than M2+ so O-H bond breaks more easily.
HYDROLYSIS OF M2+(aq)
[M(H2O)6]2+ [M(H2O)5(OH)]+ + H+
[M(H2O)5(OH)]+ [M(H2O)4(OH)2] + H+
[M(H2O)4(OH)2] [M(H2O)3(OH)3]- + H+
[M(H2O)3(OH)3]- [M(H2O)2(OH)4]2- + H+
[M(H2O)2(OH)4]2- [M(H2O)(OH)5]3- + H+
[M(H2O)(OH)5]3- [M(OH)6]4- + H+
HYDROLYSIS OF M3+(aq)
[M(H2O)6]3+ [M(H2O)5(OH)]2+ + H+
[M(H2O)5(OH)]2+ [M(H2O)4(OH)2]+ + H+
[M(H2O)4(OH)2]+ [M(H2O)3(OH)3] + H+
[M(H2O)3(OH)3] [M(H2O)2(OH)4]- + H+
[M(H2O)2(OH)4]- [M(H2O)(OH)5]2- + H+
[M(H2O)(OH)5]2- [M(OH)6]3- + H+
METAL AQUA IONS + OH-
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AQUA IONS + OH-
[M(H2O)6]2+ + 2 OH- → [M(H2O)4(OH)2] + 2 H2O
M2+(aq) + 2 OH-(aq) → M(OH)2(s)
[Cu(H2O)6]2+ + 2 OH- → [Cu(H2O)4(OH)2] + 2 H2O
Cu2+(aq) + 2 OH-(aq) → Cu(OH)2(s)
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[M(H2O)6]2+ + 2 OH- → [M(H2O)4(OH)2] + 2 H2O
M2+(aq) + 2 OH-(aq) → M(OH)2(s)
[Co(H2O)6]2+ + 2 OH- → [Co(H2O)4(OH)2] + 2 H2O
Co2+(aq) + 2 OH-(aq) → Co(OH)2(s)
AQUA IONS + OH-
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[M(H2O)6]2+ + 2 OH- → [M(H2O)4(OH)2] + 2 H2O
M2+(aq) + 2 OH-(aq) → M(OH)2(s)
[Fe(H2O)6]2+ + 2 OH- → [Fe(H2O)4(OH)2] + 2 H2O
Fe2+(aq) + 2 OH-(aq) → Fe(OH)2(s)
AQUA IONS + OH-
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[M(H2O)6]3+ + 3 OH- → [M(H2O)3(OH)3] + 3 H2O
M3+(aq) + 3 OH-(aq) → M(OH)3(s)
[Al(H2O)6]3+ + 3 OH- → [Al(H2O)3(OH)3] + 3 H2O
Al3+(aq) + 3 OH-(aq) → Al(OH)3(s)
AQUA IONS + OH-
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[M(H2O)6]3+ + 3 OH- → [M(H2O)3(OH)3] + 3 H2O
M3+(aq) + 3 OH-(aq) → M(OH)3(s)
[Fe(H2O)6]3+ + 3 OH- → [Fe(H2O)3(OH)3] + 3 H2O
Fe3+(aq) + 3 OH-(aq) → Fe(OH)3(s)
AQUA IONS + OH-
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[M(H2O)6]3+ + 3 OH- → [M(H2O)3(OH)3] + 3 H2O
M3+(aq) + 3 OH-(aq) → M(OH)3(s)
[Cr(H2O)6]3+ + 3 OH- → [Cr(H2O)3(OH)3] + 3 H2O
Cr3+(aq) + 3 OH-(aq) → Cr(OH)3(s)
AQUA IONS + OH-
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AMPHOTERIC NATURE
Amphoteric = reacts with acids and bases
[Cu(OH)2]XS OH-
[Cu(H2O)6]2+
XS H+
[Fe(OH)2][Fe(H2O)6]2+
[Co(OH)2][Co(H2O)6]2+
[Fe(OH)3][Fe(H2O)6]3+
[Cr(OH)3] [Cr(OH)6]3-[Cr(H2O)6]3+
[Al(OH)3] [Al(OH)4]-[Al(H2O)6]3+
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[Cr(H2O)3(OH)3] [Cr(OH)6]3-
Cr(OH)3(s) → [Cr(OH)63-](aq)
AQUA IONS + XS OH-
[Al(H2O)3(OH)3] [Al(H2O)2(OH)4]-
Al(OH)3(s) → [Al(OH)4-](aq)
+ 3 OH- + 3 H2O
+ 3 OH-(aq)
+ OH- + H2O
+ OH-(aq)
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METAL AQUA IONS + NH3
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[M(H2O)6]2+ + 2 NH3 → [M(H2O)4(OH)2] + 2 NH4+
M2+(aq) + 2 OH-(aq) → M(OH)2
[Cu(H2O)6]2+ + 2 NH3 → [Cu(H2O)4(OH)2] + 2 NH4+
Cu2+(aq) + 2 OH-(aq) → Cu(OH)2
NH3(aq) + H+(aq) → NH4+(aq)
NH3(aq) + H+(aq) → NH4+(aq)
AQUA IONS + NH3
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[M(H2O)6]2+ + 2 NH3 → [M(H2O)4(OH)2] + 2 NH4+
M2+(aq) + 2 OH-(aq) → M(OH)2
[Fe(H2O)6]2+ + 2 NH3 → [Fe(H2O)4(OH)2] + 2 NH4+
Fe2+(aq) + 2 OH-(aq) → Fe(OH)2
NH3(aq) + H+(aq) → NH4+(aq)
NH3(aq) + H+(aq) → NH4+(aq)
AQUA IONS + NH3
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[M(H2O)6]2+ + 2 NH3 → [M(H2O)4(OH)2] + 2 NH4+
M2+(aq) + 2 OH-(aq) → M(OH)2
[Co(H2O)6]2+ + 2 NH3 → [Co(H2O)4(OH)2] + 2 NH4+
Co2+(aq) + 2 OH-(aq) → Co(OH)2
NH3(aq) + H+(aq) → NH4+(aq)
NH3(aq) + H+(aq) → NH4+(aq)
AQUA IONS + NH3
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[M(H2O)6]3+ + 3 NH3 → [M(H2O)3(OH)3] + 3 NH4+
M3+(aq) + 3 OH-(aq) → M(OH)3
[Cr(H2O)6]3+ + 3 NH3 → [Cr(H2O)3(OH)3] + 3 NH4+
Cr3+(aq) + 3 OH-(aq) → Cr(OH)3
NH3(aq) + H+(aq) → NH4+(aq)
NH3(aq) + H+(aq) → NH4+(aq)
AQUA IONS + NH3
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[M(H2O)6]3+ + 3 NH3 → [M(H2O)3(OH)3] + 3 NH4+
M3+(aq) + 3 OH-(aq) → M(OH)3
[Fe(H2O)6]3+ + 3 NH3 → [Fe(H2O)3(OH)3] + 3 NH4+
Fe3+(aq) + 3 OH-(aq) → Fe(OH)3
NH3(aq) + H+(aq) → NH4+(aq)
NH3(aq) + H+(aq) → NH4+(aq)
AQUA IONS + NH3
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[M(H2O)6]3+ + 3 NH3 → [M(H2O)3(OH)3] + 3 NH4+
M3+(aq) + 3 OH-(aq) → M(OH)3
[Al(H2O)6]3+ + 3 NH3 → [Al(H2O)3(OH)3] + 3 NH4+
Al3+(aq) + 3 OH-(aq) → Al(OH)3
NH3(aq) + H+(aq) → NH4+(aq)
NH3(aq) + H+(aq) → NH4+(aq)
AQUA IONS + NH3
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METAL AQUA IONS + CO32-
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AQUA IONS + CO32-
[M(H2O)6]2+ + CO32- → [M(H2O)6]CO3
M2+(aq) + CO32-(aq) → MCO3(s)
[Cu(H2O)6]2+ + CO32- → [Cu(H2O)6]CO3
Cu2+(aq) + CO32-(aq) → CuCO3(s)
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AQUA IONS + CO32-
[M(H2O)6]2+ + CO32- → [M(H2O)6]CO3
M2+(aq) + CO32-(aq) → MCO3(s)
[Co(H2O)6]2+ + CO32- → [Co(H2O)6]CO3
Co2+(aq) + CO32-(aq) → CoCO3(s)
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AQUA IONS + CO32-
[M(H2O)6]2+ + CO32- → [M(H2O)6]CO3
M2+(aq) + CO32-(aq) → MCO3(s)
[Fe(H2O)6]2+ + CO32- → [Fe(H2O)6]CO3
Fe2+(aq) + CO32-(aq) → FeCO3(s)
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AQUA IONS + CO32-
2 [M(H2O)6]3+ + 3 CO32- → 2 [M(H2O)3(OH)3] + 3 H2O + 3 CO2
2 H+ + CO32- → H2O + CO2
2 [Cr(H2O)6]3+ + 3 CO32- → 2 [Cr(H2O)3(OH)3] + 3 H2O + 3 CO2
[M(H2O)6]3+ provides 3 H+ ions
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AQUA IONS + CO32-
2 [M(H2O)6]3+ + 3 CO32- → 2 [M(H2O)3(OH)3] + 3 H2O + 3 CO2
2 H+ + CO32- → H2O + CO2
[M(H2O)6]3+ provides 3 H+ ions
2 [Fe(H2O)6]3+ + 3 CO32- → 2 [Fe(H2O)3(OH)3] + 3 H2O + 3 CO2
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AQUA IONS + CO32-
2 [M(H2O)6]3+ + 3 CO32- → 2 [M(H2O)3(OH)3] + 3 H2O + 3 CO2
2 H+ + CO32- → H2O + CO2
[M(H2O)6]3+ provides 3 H+ ions
2 [Al(H2O)6]3+ + 3 CO32- → 2 [Al(H2O)3(OH)3] + 3 H2O + 3 CO2
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SUBSTITUTION BY Cl-
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[Co(H2O)6]2+ + 4 Cl- [CoCl4]2- + 6 H2O
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SUBSTITUTION by larger ligands
Cl- bigger than O of H2O – only four Cl-’s fit around Mn+
Cl- O
H
H
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[Cu(H2O)6]2+ + 4 Cl- → [CuCl4]2- + 6 H2O
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SUBSTITUTION BY NH3
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SUBSTITUTION by similar sized ligands
[Co(H2O)6]2+ + 6 NH3 → [Co(NH3)6]2+ + 6 H2O
[Co(NH3)6]2+
air
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SUBSTITUTION by similar sized ligands
[Co(H2O)6]2+ + 6 NH3 → [Co(NH3)6]2+ + 6 H2O
[Co(NH3)6]2+
air
[Cu(H2O)6]2+ + 4 NH3 → [Cu(NH3)4(H2O)2]2+ + 4 H2O
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SUBSTITUTION by similar sized ligands
[Co(H2O)6]2+ + 6 NH3 → [Co(NH3)6]2+ + 6 H2O
[Co(NH3)6]2+
air
[Cu(H2O)6]2+ + 4 NH3 → [Cu(NH3)4(H2O)2]2+ + 4 H2O
[Fe(H2O)6]2+
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SUBSTITUTION by similar sized ligands
[Co(H2O)6]2+ + 6 NH3 → [Co(NH3)6]2+ + 6 H2O
[Co(NH3)6]2+
air
[Cu(H2O)6]2+ + 4 NH3 → [Cu(NH3)4(H2O)2]2+ + 4 H2O
[Fe(H2O)6]2+
[Fe(H2O)6]3+
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SUBSTITUTION by similar sized ligands
[Co(H2O)6]2+ + 6 NH3 → [Co(NH3)6]2+ + 6 H2O
[Co(NH3)6]2+
air
[Cu(H2O)6]2+ + 4 NH3 → [Cu(NH3)4(H2O)2]2+ + 4 H2O
[Fe(H2O)6]2+
[Fe(H2O)6]3+
[Cr(H2O)6]3+ + 6 NH3 → [Cr(NH3)6]3+ + 6 H2O
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SUBSTITUTION by similar sized ligands
[Co(H2O)6]2+ + 6 NH3 → [Co(NH3)6]2+ + 6 H2O
[Co(NH3)6]2+
air
[Cu(H2O)6]2+ + 4 NH3 → [Cu(NH3)4(H2O)2]2+ + 4 H2O
[Fe(H2O)6]2+
[Fe(H2O)6]3+
[Cr(H2O)6]3+ + 6 NH3 → [Cr(NH3)6]3+ + 6 H2O
[Al(H2O)6]3+
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SUMMARY 1
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SUMMARY
[M(H2O)6]3+
M(OH)3
OH- / NH3 H+
[Cr(NH3)6]3+
XS NH3
[Cr(OH)6]3-
[Al(OH)4]-
XS OH-
M(OH)3 + CO2
CO32-
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SUMMARY
[M(H2O)6]2+
M(OH)2
OH- / NH3 H+
[Co(NH3)6]2+
XS NH3
XS OH-
MCO3
CO32-
[Cu(NH3)4(H2O)2]2+
No reaction
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CHELATE EFFECT
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THE CHELATE EFFECT
[Cr(H2O)6]3+ + 3 en → [Cr(en)3]3+ + 6 H2O
[Cr(H2O)6]3+ + EDTA4- → [Cr(EDTA)]- + 6 H2O
4 particles → 7 particles
2 particles → 7 particles
• Small H in substitution reactions.
• Big increase in entropy (large +ve S).
• Products are thermodynamically more stable than reactants – known as the “chelate effect”
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REDOX REACTIONS
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2 CrO42- + 2 H+ Cr2O7
2- + H2OCr +6yellow
Cr +6orange
oxidation state species colour
Cr +6 Cr2O72- orange
REDUCTION OF Cr(+6)
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2 CrO42- + 2 H+ Cr2O7
2- + H2OCr +6yellow
Cr +6orange
oxidation state species colour
Cr +6 Cr2O72- orange
Cr +3 Cr3+ [Cr(H2O)6]3+ green
REDUCTION OF Cr(+6)
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2 CrO42- + 2 H+ Cr2O7
2- + H2OCr +6yellow
Cr +6orange
oxidation state species colour
Cr +6 Cr2O72- orange
Cr +3 Cr3+ [Cr(H2O)6]3+ green
Cr +2 Cr2+ [Cr(H2O)6]2+ blue
Reduced by Zn/H+ from Cr +6 → +3 → +2
REDUCTION OF Cr(+6)
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Easier to oxidise (take electrons) from –ve species.
Easier to reduce (add electrons) to +ve species.
Cr(+3) – OXIDATION IN ALKALINE CONDITIONS
[Cr(OH)3] [Cr(OH)6]3-[Cr(H2O)6]3+
in acidic conditions in very alkaline conditions
e.g. Cr(+3)
in alkaline conditions
[Cr(H2O)6]2+
Cr(+2)
Zn / HCl
CrO42-
Cr(+6)
H2O2 / OH-
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CrO42-+ 4 H2O + 3 e- Cr(OH)3 + 5 OH- E = -0.13 V
Cr2O72- + 14 H+ + 6 e- 2 Cr3+ + 7 H2O E = +1.33 V
Cr(+3) – OXIDATION IN ALKALINE CONDITIONS
Cr(+6) Cr(+3)
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Co(+2) – OXIDATION IN ALKALINE CONDITIONS
Co(OH)2
Made from Co2+ in alkaline conditions
air
Co(OH)3
Co(+2) Co(+3)
[Co(NH3)6]2+
Made from Co2+ in alkaline (NH3)
conditions
air
Co(+2) Co(+3)
[Co(NH3)6]3+
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M(OH)2 – OXIDATION IN ALKALINE CONDITIONS
Co(OH)2
air
Co(OH)3
Co(+2) Co(+3)
Fe(OH)2
air
Fe(OH)3
Fe(+2) Fe(+3)
Fe(OH)3 + e- Fe(OH)2 + OH- E = -0.56 V
Fe3+ + e- Fe2+ E = +0.77 V
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SUMMARY 2
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SUMMARY
[M(H2O)6]3+ M(OH)3
OH- / NH3
H+
[Cr(NH3)6]3+
XS NH3
[Cr(OH)6]3-
[Al(OH)4]-
XS OH-
H2O2
[Cr(H2O)6]3+
[Fe(H2O)6]3+
[Al(H2O)6]3+
Cr(OH)3
Fe(OH)3
Al(OH)3
CrO42-
CO32-
+ CO2
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SUMMARY
[M(H2O)6]2+ M(OH)2
OH- / NH3
H+
[Cu(H2O)2(NH3)4]2+
XS NH3
[CuCl4]2-
[CoCl4]2-
XS OH-
[Cu(H2O)6]2+
[Co(H2O)6]2+
[Fe(H2O)6]2+
Cu(OH)2
Co(OH)2
Fe(OH)2
[Co(NH3)6]2+
air
[Co(NH3)6]3+
air
Co(OH)3
Fe(OH)3
Cl-
CO32-
CuCO3
CoCO3
FeCO3© www.chemsheets.co.uk A2 042 20-Jul-12
SUMMARY
[M(H2O)6]2+
M(OH)2
OH- / NH3 H+
[Co(NH3)6]2+
XS NH3
XS OH-
MCO3
CO32-
[Cu(NH3)4(H2O)2]2+
No reaction
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