Transition Metals Flashcards
Transition elements
An element that forms at least one stable one with a partially filled d sub shell
Name two elements that are not transition metals
Scandium SC3+
Zinc Zn2+
Electronic configuration of chromium
Is2, 2s2,2p6,3s2,3p6,4s1,3d5
E.C of copper
1s2, 2s2, 2p6,3s2,3p6,4s1,3d10
Properties of transition metal
Form complex ions
Coloured ion
Catalytic properties
Variable oxidation state
Coordinate bond
Covalent bond where both electrons are donated by 1 atom only
Ligand
Molecule or ion with a lone pair of electrons that form a coordinate bond with central metal ion
Bidentate ligand
Molecule or ion with 2 lone pair of electrons on two different atoms that each form a coordinate bond with central metal ion
Coordination number
The number of coordinate bonds formed with central metal ion
Complex ion
The central metal ion surrounded by ligands
Monodetate ligands
Each have 1 coordinate bond
H2O
NH3
CN-
Cl-
Bidentate ligand
Each ligand form 2 coordinate bonds
Ethane-1,2-diamine
Ethanedioate C2O4 2-
Multidentate ligands
Each ligand form more than 2 coordinate bond
EDTA4-
EDTA4- can form six coordinate bonds, 2 coordinate bonds with N atoms and 4 coordinate bonds from O- atoms
Chelate effect
When monodentate ligand is substituted by a Bidentate or a multidentate ligand
Results in increasing number of moles on RHS
Increases entropy
Why a reaction is feasible
Entropy change is zero
Because same number of bonds are broken and formed
More molecules on RHS
Entropy increases
Delta G is negative
Heamoglobin
4 coordinate bonds between Fe2+ and N atoms in beam structure ( square planer)
1 coordinate bond between Fe2+ and O2 molecule
1 coordinate bond between Fe2+ and globin protein
Why CO is toxic
O2 forms a coordinate bond with Fe2+ in Haemoglobin enabling oxygen to be transported around the body
CO is toxic as it bonds more strongly and permanently to Fe2+ in heamoglobin
This prevents O2 binding to Fe 2+ causing suffocation
Octahedral complexes
Ligands of 4 one type and 2 of another type can form octahedral complexes
Can also form cis and trans isomers
Square planer
PtCl2(NH3)2
Can form cis and trans isomer
Cis platin
Bonds to DNA cancer cell and stop cell replication
The two Cl- ions on Cisplatin are substituted for 2 N atoms in the adjacent guanine bases
Roy light
Low energy
Big light
High energy
kMNO4 clour
Purple
( absorbs yellow and Green )
CuSO4
Blue
Ground state
In pure transition metal atom all d orbitals have equal energy. This is called ground state
Difference in energy
E=hc/lemda
H= Planck constant
c is speed of light
Lemda is wavelengths of light
Big Energy
Abosob blue indigo and voilent
Reflect red orange and yellow
Compound looks orange/red
Small energy
ROY absorbs
BIV reflected
Compound looks blue\ purple
Change in E could be because of
LOCOS
Change in ligand
Change in oxidation state
Change is coordination number
Change in shape of complex
Colour of VO2 +
Yellow
VO 2+
Blue
V3+
Green
V2+
Voilent
Fe2+
Green
Fe 3+
Pale yellow
Co2+
Brown
Co3+
Yellow
Cr 2+
Blue
Cr3+
Red- voilent
Heterogeneous catalysis
Catalyst is in diffenent phase as reactants
Homogeneous catalysis
Reactant is in same phase as catalyst
How does a catalyst work
Reactants adsorb onto the surface of catalyst on active site
Reaction occurs on the surface of catalyst
Product desorb from surface of catalyst
How to make catalyst efficient
Increase the surface area
Spread catalyst over the inert support of medium
How can poisoning occur in catalyst
Impurities Allan block the active site
This prevent the reactants form adsorbing
Purifying the reactants is the best way to prevent poisoning
Heterogeneous catalysis examples
Making ammonia is Harber process
Catalysed by solid iron
N2 + 3H2 = 2NH3
Making sulphuric acid in contact process
Catalysed by vanadium oxide V2O5
Contact process
SO2 + V2O5 = SO3 + V2O4
2 V2O4 + O2 = 2V2O5
Overall reaction
SO2 + O2= SO3
SO3 can react with water to form sulphuric acid
Menufacturing of methanol
Catalysed by chromium oxide
CH4 + H2O = CO + 3H2
CO + 2H2 =CH3OH
Why transition metals act as catalyst
Because they have variable oxidation states
Why group 1 elements don’t act as catalyst
Because they have only one oxidation state
Homogenous catalysis examples
Peroxodisulfate ions oxidise iodide ions to iodine. reaction is catalysed by Fe2+ ions.
Fe2 +
Fe3+
MnO4-
Mn2+
Cr2O7 2-
Cr3+
C2O4 2-
CO2
Zn
Zn2+
S2O8 2-
SO4 2-
I-
I2
Mn3+
Mn2+
Co2+
Co3+
VO2+
VO^2+
Why uncatalysed reactions have higher Ea?
Both both ions are negative and they repel each other
Autocatalysis
It is when one product of the reaction catalyses the reaction.
example of autocatalysis
oxidation of ethandioic acid by manganate (VII) ions
Graph for autocatalysis
rate starts off slowly as there is no catalysts initailly.
The two negatively charged reactants collide with a higher Ea.
Then some Mn^2+ is formed , the rate of reaction is being increased as Mn^2+ acts as a catalyst.
The rate then decreases and levels off as all the reactants get used up.
reation of MnO4^- to Fe^2+
from deep purple to colorless
Why HCl should never be used if transition metal redox reaction is taking place in acidic conditions?
Because both MnO4^- and Cr2O7^2- can oxidese Cl- ions to Cl2. Cl2 gas poses obvious safely risks. also effect titration effect, and make it seem like more oxidising agent has been used than it should be
sulphuric acid should be used to acidify the solutions.
Describe briefly how colorimeter can be used to to determine the concentration of this solution ?
Make some known concentrations
Plot a graph of absorbance vs concentration
Read/compare the unknown concentration from calibration curve.
Why reactants should be purified before they come into contact with catalyst.
So catalyst are not poisoned
