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Chemistry A Level > Chapter 23 - Transition Metals > Flashcards

Chapter 23 - Transition Metals Flashcards

1
Q

What are the common properties of metals

A

Conduct electricity and heat
Strong
Hard
Shiny
High MP and BP

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2
Q

What block are the transition metals in

A

d-block

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3
Q

What is a transition metal

A

It is a metal that forms at least 1 stable ion with a partially filled d-shell of electrons

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4
Q

What are the general properties of transition metals

A

Variable oxidation state
Catalysis
Complex Formation
Colour

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5
Q

What can transition metals form

A

Complex ions

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6
Q

How are complex ions formed

A

When a transition metal or ion becomes surrounded by ligands
The ligands form coordinate bonds by donating electron pairs

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7
Q

What are ligands

A

A cluster of molecules or ions that are bonded to the metal in a complex ion
Can be neutral or ionic

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8
Q

What is the coordination number

A

The number of bonds around the central metal atom or ion

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9
Q

What are examples of neutral ligands

A

H2O
NH3
CO

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10
Q

What are examples of ionic ligands

A

Cl-
OH-
CN-

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11
Q

In complex formations, what do the ligands function as

A

Lewis bases

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12
Q

What are Lewis Bases

A

Electron pair donors

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13
Q

What are Lewis acids

A

Electron pair acceptor

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14
Q

In complex formations, what does the transition metal act as

A

Lewis Acid

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15
Q

What are the 4 parts of the names of complexes

A

Prefix
Type of ligand
Name of metal
Oxidation number of metal

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16
Q

What are the prefixes of complexes

A

Hexa = 6 ligands
Tetra = 4 ligands
Di = 2 ligands

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17
Q

What are the examples of ligands

A

H2O = aqua
Cl- = chloro
NH3 = ammine
OH- = hydroxo
CN- = cyano

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18
Q

What are the names of metals for positively charged complexes
Vanadium
Chromium
Manganese
Iron
Cobalt
Nickel
Copper
Zinc
Silver

A

Vanadium
Chromium
Manganese
Iron
Cobalt
Nickel
Copper
Zinc
Silver

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19
Q

What are the names of metals for negatively charged complexes
Vanadium
Chromium
Manganese
Iron
Cobalt
Nickel
Copper
Zinc
Silver

A

Vanadate
Chromate
Manganate
Ferrate
Cobaltate
Nickelate
Cuprate
Zincate
Argentate

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20
Q

How are the oxidation number of the metal expressed

A

In roman numerals

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21
Q

What determines the shape of a complex

A

The coordination number

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22
Q

How are ligands classified

A

By the number of coordinate bonds they are able to form in complexes

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23
Q

What are the types of ligands

A

Unidentate
Bidentate
Multidentate

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24
Q

What are unidentate ligands

A

Ligands that bond through 1 donor atom
e.g. H2O, NH3, Cl-

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25
What are bidentate ligands
Ligands that bond through 2 donor atoms
26
What are the 2 bidentate ligands
1,2 - diaminoethane (NH2 CH2 CH2 NH2) ethanedioate ion (C2O4 2-)
27
What are multidentate ligands
Ligands that bond through many donor atoms e.g. EDTA
28
What can complex ions exhibit
Geometric and optical isomerism
29
When can optical isomerism be displayed
Octahedral shape with 3 bidentate ligands
30
When can geometric isomerism (cis-trans isomerism) happen
Octahedral shape with 4 of the same ligand and 2 of a different ligand Square planar with 2 ligands of the same and 2 different ligands
31
What is a compound with a square planar shape
Cisplatin [Pt(NH3)2Cl2]
32
What type of geometric isomerism is Cis
The 2 different ligands are adjacent to each other
33
What type of geometric isomerism is trans
The 2 different ligands are opposite each other
34
How can chlorine atoms exist in complex salts
Chlorine ligands or free chloride ions e.g. Cr(H2O)6 Cl3
35
How can you determine if a chlorine atom is in a complex or a free chloride ion
Silver Nitrate solution Free chloride ions will form white silver chloride precipitate Chlorine ligands won't react The number of moles of AgCl formed per mole of complex shows how many atoms of chlorine are free
36
What are chelates
They are complexes containing multidentate ligands
37
What is the order of ligands ability to bind from best to worst
Multidentate Bidentate Unidentate
38
What can transition metals form
coloured complexes
39
Why are transition metal complexes coloured
They are able to absorb visible light The colour we observe depends on the wavelengths absorbed by the complex
40
What colour is the complex when a particular colour is absorbed
Its complementary colour is reflected
41
How are transition metals able to absorb light
When ligands surround the central ion it causes the d-orbitals to split into 2 slightly different energy levels The electrons absorb energy in the visible region, they move from 1 d-orbital to a higher one This causes a combination of the non absorbed colours to form the coloured compound
42
How is the energy absorbed found (the difference between the lower and higher energy levels)
Using Planck's equation AE = hv h= Planck's constant v=frequency of light absorbed
43
What affects the size of the energy gap
The transition metal Type of ligand attached Co-ordination number in the complex Oxidation state of the transition metal
44
What does a colorimeter measure
The absorption of visible light
45
What can data from a colorimeter be used to do
Construct a calibration curve, measuring the absorbance of solutions of known concentration and then using this to find the concentration of unknown solution based on their absorbance
46
What is required sometimes for complexes with place colours
Might be necessary to add a different ligand to intensify the colour
47
What can colourmetry also be used for
Used to find the ratio of metal ions to ligand in a a complex
48
What are the 2 ways to do a colorimetry experiment to find concentration of unknown solutions
Keep the volume of the metal ion constant and adding different amounts of ligands Varying the volume of both solutions but keep the final volume constant
49
What will happen in the experiment
When the volume of metal ion and ligand are mixed in the same ratio as they are in the complex, the absorbance will peak
50
What are the most common oxidation states of each transition metal Ti V Cr Fe Co Ni Cu Zn
Ti - 4 V - 4 and 5 Cr - 2,3 and 6 Fe - 2 and 3 Co - 2 and 3 Ni - 2 Cu - 2 Zn - 2
51
What do the lower oxidation states exist as
Simple ions
52
What do the higher oxidation states exist as
In compounds with very electronegative ions
53
What is reduction
Gain of electrons
54
What is a reducing agent
Loss of electrons
55
What is oxidation
Loss of electrons
56
What is an oxidising agent
Gains electrons
57
What does the ease of changing an oxidation state of a TM depend on
pH and the ligands present
58
What conditions is it easier to oxidise a transition metal
alkaline
59
What conditions is it easier to reduce a transitional metal
acidic
60
What is a catalyst
A substance which alters the rate of a chemical reaction but is unchanged at the end
61
How do catalysts work
They provide an alternative reaction route with a lower activation energy
62
What do catalysts not affect
AG AH position of equilibrium
63
Why can transition metals be used as catalysts
Their partially filled d-orbitals allow them to alternatively accept and reject electrons by changing oxidation states This allows them to help transfer electrons
64
What are the 2 types of catalysts
Homogeneous Heterogeneous
65
What are homogeneous catalysts
Where the catalyst is in the same phase
66
What are heterogeneous catalysts
Catalysts in a different phase to the reactants
67
What processes involve heterogeneous catalysis
Haber process Contact process Making methanol
68
How do heterogeneous catalysts work
They absorb reactants onto the surface of catalyst, forming weak bonds Reaction occurs The product molecules are desorbed from surface and diffuse away
69
How can the absorption of reactants increase the rate of reaction
Absorption concentrates the reactants, brings them closer It may weaken bonds within the reactants It may position the molecules in a favourable orientation
70
How are catalysts used efficiently
Increase surface area Spreading the catalyst onto an inert support medium - increases surface to mass ratio
71
Why don't catalysts last forever
The finely divided catalyst can simply come off the support medium The catalyst becomes poisoned
72
What is catalyst poisoning
When the surface becomes covered with unwanted impurities blocking active sites
73
How is a catalyst used for the Haber process
Iron catalyst N2 + 3H2 -> 2NH3 Becomes poisoned with sulphur
74
What is the contact process
It makes sulphuric acid The key step is: 2SO2 + O2 -> 2SO3 Catalysed by Vanadium oxide
75
What are the 2 steps to catalyse the contact process
SO2 + V2O5 -> SO3 + V2O4 2V2O4 + O2 -> 2V2O5
76
What are the reaction for making methanol
CH4 + H2O -> CO + 3H2 It is manufactored from sythesis gas ( CO and H2) CO + 2H2 -> CH3OH Cr2O3 catalyst
77
How does homogeneous catalysts work
They can act as homogeneous catalysts for reactions in solution due to their variable oxidation number This allows them to form intermediate species which have lower activation energy's
78
What is the reaction between iodide and peroxodisulphate and how is it catalysted
2I- + S2O8 2- -> I2 + 2SO4 2- Fe catalyst S2O8 2- + 2Fe2+ -> 2SO4 2- + 2Fe3+ 2Fe3+ + 2I- -> 2Fe2+ + I2
79
Why is the non-catalysed reaction of iodide with peroxodisulphate so slow
It involves the collision of 2 negatively charged ions
80
What is autocatalysis
It is where one of the products of a reaction is a catalyst for the reaction
81
What is the reaction of ethanedioate with manganate ions
2MnO4- + 16H+ + 5C2O4 2- -> 2Mn2+ + 10CO2 + 8H2O
82
What catalyst is there in the ethanedioate with manganate ions
Mn2+
83
What are the equations of the catalyst reacting with the reactants in the ethanedioate with manganate ions
MnO4- + 4Mn2+ + 8H+ -> 5Mn3+ + 4H2O 2Mn3+ + C2O4 2- -> 2Mn2+ + 2CO2 2MnO4- + 16H+ + 5C2O4 2- -> 2Mn2+ + 10CO2 + 8H2O
84
What is the reaction between chromate ions and iron 2+
Cr2O7 2- + 14H+ + 6Fe2+ -> 2Cr3+ + 7H2O + 6Fe3+
85
What is the reaction between manganate ions and iron 2+
MnO4- + 8H+ + 5Fe2+ -> Mn2+ + 4H2O + 5Fe3+
86
What is the equation for frequency of light
speed of light/wave length
87
Why in a calorimetry experiment does the container for each sample the same
Absorption depends on path length of light

Chemistry A Level (20 decks)

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