© A2 042 20-Jul-12. Metal aqua ions Hydrolysis Metal aqua ions + OH - Metal aqua ions + NH 3 Metal aqua ions + CO 3 2- Substitution

© www.chemsheets.co.uk A2 042 20-Jul-12

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


METAL AQUA IONS


METAL AQUA IONS

e.g.[Cu(H2O)6]2+

OH2

Cu

OH2

H2O OH2

H2O OH2

2+


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








REACTIONS

1) Hydrolysis O-H bond in H2O ligand breaks

2) Substitution M-ligand bond breaks

3) Redox change in oxidation state of M


HYDROLYSIS


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-


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)



[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-



[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-



[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-



[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-



[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-


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+


[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)


METAL AQUA IONS + NH3



[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)


AQUA IONS + NH3



[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



AQUA IONS + NH3



[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



AQUA IONS + NH3



[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



AQUA IONS + NH3



[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



AQUA IONS + NH3



[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



AQUA IONS + NH3


METAL AQUA IONS + CO32-



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)



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)



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)



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



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 [Fe(H2O)6]3+ + 3 CO32- → 2 [Fe(H2O)3(OH)3] + 3 H2O + 3 CO2



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 [Al(H2O)6]3+ + 3 CO32- → 2 [Al(H2O)3(OH)3] + 3 H2O + 3 CO2


SUBSTITUTION BY Cl-


[Co(H2O)6]2+ + 4 Cl- [CoCl4]2- + 6 H2O


SUBSTITUTION by larger ligands

Cl- bigger than O of H2O – only four Cl-’s fit around Mn+

Cl- O

H

H


[Cu(H2O)6]2+ + 4 Cl- → [CuCl4]2- + 6 H2O


SUBSTITUTION BY NH3



SUBSTITUTION by similar sized ligands

[Co(H2O)6]2+ + 6 NH3 → [Co(NH3)6]2+ + 6 H2O

[Co(NH3)6]2+

air




[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




[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+




[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+




[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




[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+


SUMMARY 1


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-


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


CHELATE EFFECT


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”


REDOX REACTIONS


2 CrO42- + 2 H+ Cr2O7

2- + H2OCr +6yellow

Cr +6orange

oxidation state species colour

Cr +6 Cr2O72- orange

REDUCTION OF Cr(+6)


2 CrO42- + 2 H+ Cr2O7

2- + H2OCr +6yellow

Cr +6orange



Cr +3 Cr3+ [Cr(H2O)6]3+ green

REDUCTION OF Cr(+6)


2 CrO42- + 2 H+ Cr2O7

2- + H2OCr +6yellow

Cr +6orange



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)


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-


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)


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+


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


SUMMARY 2


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


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


Documents

© A2 042 20-Jul-12. Metal aqua ions Hydrolysis Metal aqua ions + OH - Metal aqua ions + NH 3 Metal aqua ions + CO 3 2- Substitution