Transition metals

heterogenous catalysts

catalysts in a different state than reactants
works in 3 stages:
1. adsorption of reactants onto active sites of catalyst
2. bonds broken, reaction occurs
3. desorption, reactants detach from active sties

what affects longevity of catalysts

surface area (whether mesh used, small or large chunks)
poisoning (via blocking of active sites by sulfates)

transition metals definition

metals which have an incomplete d subshell in one of their stable ion forms

which metals are not transition metals

zinc, copper

which transition metals form square planar

platinum, nickel

complex ion definition

containing a central metal ion bonded to ligands

what ligands allow optical isomerism

bidentate ligands (e.g. NH2CH2CH2NH2, OOCCOO)

why are transition metals coloured

have incomplete d subshells. d orbitals have different energies, when electrons are promoted to the excited state, the metal absorbs a wavelength of light, the remaining wavelengths of light are the colour observed (complementary colour) as these lights are reflected

how would one use a calibration graph to find concentration

measure absorbance for a range of known contentrations
plot a graph of absorbance against conc
read concentration from absorbance value

why is the shape different when Cl- used as ligand

Cl- is a bigger ligand, only fits 4 around metal
therefore either tetrahedral or sq planar

chelate effect

when bidentate/multidentate ligands replace monodentate ligands a more stable complex is formed, due to an increase in entropy as more particles formed

why do some complex ions exist with low pH’s?

high charge density
high polarising effect
weakens O-H bonds releasing H+ ions

why are Cu2+ ions yellow?

light of opposing wavelength absorbed
only yellow light reflected

autocatalysis

when one of the products acts as a catalyst

2[M(H2O)6]3+ + 3CO3 2-

2[M(H2O)3(OH)3] + 3H2O + 3CO2

[M(H2O)6]3+ +3OH-

[M(H2O)3(OH)3] +3H2O

[M(H2O)6]3+ + 3NH3

[M(H2O)3(OH)3] +3H2O + 3NH4+

[M(H2O)6]2+ +2OH-

[M(OH)2(H2O)4] +2H2O

[M(H2O)6]2+ + CO3 2-

MCO3 + 6H2O

[Cu(H2O)6]2+ + 4NH3

[Cu(NH3)4(H2O)2] +2H2O + 2OH-

[Fe(H2O)6]2+ + 6NH3

Fe(OH)2 + 6NH4-

contact process: vanadium catalyst 2 equations

V2O5 + SO2 → V2O4 + SO3
V2O4 + 0.5O2 → V2O5

autocatalysis: Mn 2+ C2O4 2- example

4Mn²⁺ + MnO₄^- + 8H⁺ → 5Mn³⁺ + 4H₂O
2Mn³⁺ + C₂O₄^2- → 2CO₂ + 2Mn²⁺

iron catalysis equations

2Fe²⁺ + S₂O₈^2- → 2SO₄^2- + 2Fe³⁺
2Fe³⁺ + 2 I- → 2 Fe²⁺ + I₂
no catalyst: S₂O₈^2- + 2I^- → 2SO₄^2- + I₂

Vanadium Colours

2+ → purple

3+ → green

4+ → blue

5+ → yellow

Vanadium and Water

2+/3+ → [V(H2O)6]x+

4+ → [VO(H2O)5]2+

5+ → [VO2(H2O4)]+

why are different metal complexes different colours

metal ion, ligands bonded, coordination number, oxidation state