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What is a transition metal
A metal that can form one or more stable ions with a partially filled d sub-shell
What are the chemical properties of transition metals.
Can form complex ions
They form coloured ions
Good catalysts
variable oxidative states
What is a complex ion
a central metal atom or ion surrounded by co-ordinately bonded ligands
What is a ligand
an atom ion or molecule that donates a pair electrons to a central transition metal ion.
what are bidentate ligands
can form two co-ordinate bonds
What’s the reaction between [Cu(H2O)6]2+ and hydrochloric acid, what is the colour change?
[Cu(H2O)6]2+ + 4Cl- → [CuCl4]2- + 6H2O
Blue → green → yellow
What’s the reaction between [Co(H2O)6]2+ and hydrochloric acid, what is the colour change?
[Co(H2O)6]2+ + 4Cl- → [CoCl4]2- + 6H2O
Red → blue
What’s the reaction between [Cu(H2O)6]2+ and ammonia , what is the colour change? (partial and full equation)
[Cu(H2O)6]2+ + 6NH3 → [Cu(NH3)4(H2O)2]2+ + 4H2O
OR
[Cu(H2O)6]2+ + 2NH3 → [Cu(OH)2(H2O)4]2+ + 2NH4
[Cu(OH)2(H2O)4]2+ + 4NH3 → [Cu(NH3)4(H2O)2]2+ + 2OH- + 2H2O
Blue solution → light blue precipitate → dark blue solution
What’s the maximum amount of Cl ligands a molecule can have and why?
4 Due to the fact chlorine ligands are much bigger than other ligands and so only 4 can fit around the molecule.
Examples of multidentate ligands
EDTA4-
Haem which is also an iron complex with multidentate ligands.
examples of bidentate ligands
H2NCH2CH2NH2 or ‘en’
C2O42–
How is oxygen bonded to haem
Oxygen forms a co-ordinate bond to Fe(II) in haemoglobin, enabling oxygen to be transported in the blood.
Carbon monoxide is toxic because it replaces oxygen co-ordinately bonded to Fe(II) in haemoglobin.
What is the chelate effect
Bidentate and multidentate ligands replace monodentate ligands from complexes. This is an increase in entropy → increase in free particles. The bond strength is increased → decrease in enthalpy
What complex ions can form stereoisomers
Optical isomers - Octahedral complexes with 3 bidentate ligands
Cis-Trans - Octahedral complexes with 4 monodentate ligands of one type and 2 of another, square planar with two types of ligands.
What does cisplatin look like
How is Ag+ used in tollens reagent
It forms the linear complex [Ag(NH3)2]+ When in aldehydes its reduced to form silver metal
Ag+ + e- → Ag
Why do transition metals form coloured ions
Some wavelengths are absorbed to promote/excite electrons in d-orbitals and the remaining complementary wavelengths are reflected to give the colour
What are the factors that affect the colour of the complex?
Identity of metal
Oxidation state of metal
identity of ligands
Co-ordination number
What’s the equation for working out the energy difference of the electrons
∆E = hν = hc/λ
∆E - J
ν - Hz
λ - wavelength (m)
How to determine the concentration of coloured ions in a solution
Use a colorimeter
How do you get Vanadium in oxidation states IV III and II
the reduction of vanadate (V) ions by zinc in an acidic solution.
What is the redox potential for a metal ion changing oxidation state influenced by?
Ligands: aqueous ions are surrounded by water ligands, → redox larger or smaller → how well they bind to the metal ion.
pH - redox potential is stronger in acidic solutions
maybe make flashcard on tollens reagent
What are the two types of catalyst
heterogeneous and homogeneous
What is a heterogenous catalyst
A catalyst that is in a different phase to the reactants is heterogenous catalyst. (homo is same phase)
How does a heterogeneous catalyst work
Reactants are adsorbed onto the surface / active sites
Reaction takes place/ bonds weaken
Desorption of the product
What factors affect the efficiency and lifetime of the catalyst?
Active sites blocked
Catalyst poisoned
Large surface area by using powder etc
Ideal absorption strength
Example of a heterogenous catalyst
V2O5 + SO2 → V2O4 + SO3
V2O4 + ½ O2 → V2O5
(Contact process)
(Fe is used in the Haber process)
Example of a homogenous catalyst
S2O82- + 2Fe2+ → 2Fe3+ + 2SO42-
2Fe3+ + 2I- → 2Fe2+ + I2
Examples of an autolysis catalyst
MnO4- + 4Mn2+ + 8H+ → 5Mn3+ + 4H2O
2Mn3+ + C2O42- → 2Mn2+ + 2CO2
why is the acidity of [M(H2O)6] 3+ is greater than that of [M(H2O)6] 2+
Metal 3+ ions have a much higher charge density → more polarising → more likely hydrogen released → more acidic solutions
Example of an amphoteric metal hydroxide/ what is it
Can act as both acids and bases/ dissolve in both
Aluminium hydroxide
What are the reactions and observations for the metal-aqua ion: [Cu(H2O)6]2+
OH- = [Cu(H2O)4(OH)2] blue precipitate
Excess OH- = nothing
Excess NH3 = [Cu(NH3)4(H2O)2]2+ Deep blue solution
Na2CO3 = CuCO3 Blue-green precipitate
What are the reactions and observations for the metal-aqua ion: [Fe(H2O)6]2+
OH- = [Fe(H2O)4(OH)2] green precipitate
Excess OH- = nothing
Excess NH3 = nothing
Na2CO3 = FeCO3 green precipitate
What are the reactions and observations for the metal-aqua ion: [Al(H2O)6]3+
OH- = [Al(H2O)3(OH)3] White precipitate
Excess OH- = [Al(H2O)2(OH)4] re-dissolves
Excess NH3 = Doesn’t redissolve
Na2CO3 = [Al(H2O)3(OH)3] fizzing
What are the reactions and observations for the metal-aqua ion: [Fe(H2O)6]3+
