Chemistry UNIT 5 Transition metals

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  • Created by: JessAnnB
  • Created on: 31-03-16 18:19
What period 4 d-block elements are not transition metals?
Zinc, scandium
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What is a transition metal?
It forms at least one stable ion with a partially filled d-subshell.
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What is a complex?
A central metal ion surrounded by ligands.
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What is a ligand?
A species that donates a pair of electrons to a central metal ion in a co-ordinate bond.
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Why is chromium an exception to normal electron configuration rules?
Chromium prefers to have one electron in each orbital of the 3d subshell and just one in the 4s subshell.
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Why is copper an exception to normal electron configuration rules?
Copper prefers to have a full 3d subshell and just one electron in the 4s subshell.
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What are physical properties of the transition metals?
High density, high melting and boiling points.
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Why do transition metals form a large number of complexes?
They have empty d-obitals available to accept a lone pair of electrons, the metal ion has a high charge density to attract the lone pair of electrons.
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What is a unidentate ligand?
It forms one co-ordinate bond.
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What is a ligand called if it can form more than one co-ordinate bond?
Multi-dentate ligand.
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How many co-ordinate bonds does a bi dentate ligand form?
2.
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What is co-ordination number?
The total number of co-ordinate bonds formed between the metal ion and the ligands in a complex.
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What is an example of a multi-dentate ligand?
EDTA^4-.
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How many co-ordinate bonds does EDTA have?
6.
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What is the Latin name for copper?
Cuprate.
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What is the Latin name for iron?
Ferrate.
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Which transition metal name do you use if the complex is positively charged?
The English name.
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What is the Latin name for silver?
Argentate.
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What is the Latin name for chromium?
Chromate.
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What is the Latin name for cobalt?
Cobaltate.
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What is the Latin name for vanadium?
Vanadate.
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What is the formula for hexaaquairon(||) ion?
[Fe(H2O)6]2+.
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What is the shape of a complex with two co-ordinate bonds and what is the common ion?
Linear shape, Ag+ complexes.
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What is tollen's reagent formula?
[Ag(NH3)2]+
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What are common ligands for a tetrahedral shaped complex?
Large ligands such as Cl-, Br-, I-.
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What are common metal ions in square planar complexes?
Pt2+ complexes, Ni2+ complexes.
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What is cis-platin used for and what shape is it?
Most effective anti-cancer drug, Square planar.
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What is the stereoisomerism definition as applied to complexes?
Complexes with the same formula but different arrangement of ligands in space.
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What are formulas of two square planar complexes?
[PtCl4]2-, [Ni(CN)4]2-.
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What is the shape of a complex with six co-ordinate bonds?
Octrahedral.
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What are common ligands for an octahedral shaped complex?
H2O, NH3.
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What is haemoglobin for?
It is a protein found in blood that helps to transport oxygen around the body.
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What shape is haemoglobin?
Octahedral.
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Why are oxygen molecules able to be easily given up to cells?
The Fe2+ to O2 bond is weak, as O2 is not a very good ligand.
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Why is carbon monoxide poisonous?
Carbon monoxide bonds to Fe2+ in haemoglobin irreversibly. This can destroy haemoglobin's oxygen carrying capacity.
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What equation links energy absorbed to frequency?
ΔE = hv
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When ligands bond to ions what happens to the orbitals?
Some orbitals are given more energy than others. This splits the 3d orbitals into two different energy levels.
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Why could an ion not possess the property of colour?
If you cant excite an electron as the ion has a 3d10 subshell.
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What is the colour we observe due to?
The frequencies of visible light that are not absorbed. It is the colours that are reflected that we see. These are the complecmentary colours.
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What 3 things does the exact colour of a transition metal complex depend upon?
The oxidation state of the metal, the co-ordination number of the complex and the ligands attached to the central metal ion.
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What is spectrometry used for?
To determine the concentration of a solution by measuring how much light it absorbs.
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What is a colorimeter used for?
It is a simple spectrophotometer used to analyse the colour of complexes.
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How can you work out concentration from an unknown sample?
Prepare standard solutions of known conc., measure their absorbance and plot the results. Then measure the absorbance of the unknown and read its conc. from the graph.
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What is a catalyst?
Something that speeds up the rate of a reaction by providing an alternative reaction pathway with a lower activation energy.
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Why do transition metals make good catalysts?
They can change their oxidation states by gaining or losing electrons within their d orbital.
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What is a heterogeneous catalyst?
A catalyst that is in a different phase/physical state from the reactants.
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What is the equation and catalyst for the haber process?
N2 + 3H2 ----> 2NH3, Iron catalyst.
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What is the catalyst used in the manufacture of methanol from CO and H2?
Chromium(|||) oxide.
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What is the catalyst for the contact process?
Vanadium(V) oxide.
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What is the first step of the contact process?
Vanadium(V) oxide oxidises SO2 into SO3. V2O5 + SO2 ----> V2O4 + SO3.
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What is the second step of the contact process?
The vanadium(|V) oxide reacts with oxygen to regenerate vandium(V) oxide. V2O4 + 1/2O2 ----> V2O5.
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Where does heterogenous catalysis occur on the solid catalyst?
On the surface.
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What effect does increasing the surface area of the catalyst have on the rate of the reaction and why?
Increases the rate as the number of molecules that can react at the same time increase the rate.
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What is catalytic poisoning?
Impurities in a reaction mixture may bind to the catalysts surface and block reactants from being absorbed onto active sites.
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Why does catalytic poisoning slow a reaction down?
It reduces the surface area of the catalyst available to the reactants.
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What poisons the catalyst in catalytic converters?
Lead.
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What is a homogeneous catalyst?
They are in the same physical state as the reactants. Usually it is an aqueous catalyst.
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What is made when the reactants combine with a homogeneous catalyst?
An intermediate species.
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What does the intermediate species do?
It reacts to form the products and reform the catalyst.
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What is the equation for when Fe2+ catalyses the reaction between S2O8 2- and I-?
S2O82- + 2I- -----> I2 + 2SO4 2-.
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Why is the reaction between I- and S2O82- slow without a catalyst?
The reactants are both negatively charged ions and will repel each other.
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What autocatalysis' the reaction between (MnO4)- and (C2O4)^2-?
Mn2+.
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What is an autocatalyst?
Something that is a product of the reaction and acts as a catalyst.
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Why is the reaction that is catalysed by Mn2+ slow to start with?
There isn't any Mn2+ present at the beginning of the reaction to catalyse it, so at first the rate of reaction is very slow. During this uncatalysed part the activation energy is very high.
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Card 2

Front

What is a transition metal?

Back

It forms at least one stable ion with a partially filled d-subshell.

Card 3

Front

What is a complex?

Back

Preview of the front of card 3

Card 4

Front

What is a ligand?

Back

Preview of the front of card 4

Card 5

Front

Why is chromium an exception to normal electron configuration rules?

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