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Chemistry A Level > Chapter 23 - Transition Metals > Flashcards

Chapter 23 - Transition Metals Flashcards

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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
Q

What are bidentate ligands

A

Ligands that bond through 2 donor atoms

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26
Q

What are the 2 bidentate ligands

A

1,2 - diaminoethane (NH2 CH2 CH2 NH2)
ethanedioate ion (C2O4 2-)

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27
Q

What are multidentate ligands

A

Ligands that bond through many donor atoms
e.g. EDTA

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28
Q

What can complex ions exhibit

A

Geometric and optical isomerism

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29
Q

When can optical isomerism be displayed

A

Octahedral shape with 3 bidentate ligands

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30
Q

When can geometric isomerism (cis-trans isomerism) happen

A

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

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31
Q

What is a compound with a square planar shape

A

Cisplatin
[Pt(NH3)2Cl2]

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32
Q

What type of geometric isomerism is Cis

A

The 2 different ligands are adjacent to each other

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33
Q

What type of geometric isomerism is trans

A

The 2 different ligands are opposite each other

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34
Q

How can chlorine atoms exist in complex salts

A

Chlorine ligands or free chloride ions
e.g. Cr(H2O)6 Cl3

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35
Q

How can you determine if a chlorine atom is in a complex or a free chloride ion

A

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
Q

What are chelates

A

They are complexes containing multidentate ligands

37
Q

What is the order of ligands ability to bind from best to worst

A

Multidentate
Bidentate
Unidentate

38
Q

What can transition metals form

A

coloured complexes

39
Q

Why are transition metal complexes coloured

A

They are able to absorb visible light
The colour we observe depends on the wavelengths absorbed by the complex

40
Q

What colour is the complex when a particular colour is absorbed

A

Its complementary colour is reflected

41
Q

How are transition metals able to absorb light

A

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
Q

How is the energy absorbed found
(the difference between the lower and higher energy levels)

A

Using Planck’s equation
AE = hv
h= Planck’s constant
v=frequency of light absorbed

43
Q

What affects the size of the energy gap

A

The transition metal
Type of ligand attached
Co-ordination number in the complex
Oxidation state of the transition metal

44
Q

What does a colorimeter measure

A

The absorption of visible light

45
Q

What can data from a colorimeter be used to do

A

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
Q

What is required sometimes for complexes with place colours

A

Might be necessary to add a different ligand to intensify the colour

47
Q

What can colourmetry also be used for

A

Used to find the ratio of metal ions to ligand in a a complex

48
Q

What are the 2 ways to do a colorimetry experiment to find concentration of unknown solutions

A

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
Q

What will happen in the experiment

A

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
Q

What are the most common oxidation states of each transition metal
Ti
V
Cr
Fe
Co
Ni
Cu
Zn

A

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
Q

What do the lower oxidation states exist as

A

Simple ions

52
Q

What do the higher oxidation states exist as

A

In compounds with very electronegative ions

53
Q

What is reduction

A

Gain of electrons

54
Q

What is a reducing agent

A

Loss of electrons

55
Q

What is oxidation

A

Loss of electrons

56
Q

What is an oxidising agent

A

Gains electrons

57
Q

What does the ease of changing an oxidation state of a TM depend on

A

pH and the ligands present

58
Q

What conditions is it easier to oxidise a transition metal

A

alkaline

59
Q

What conditions is it easier to reduce a transitional metal

A

acidic

60
Q

What is a catalyst

A

A substance which alters the rate of a chemical reaction but is unchanged at the end

61
Q

How do catalysts work

A

They provide an alternative reaction route with a lower activation energy

62
Q

What do catalysts not affect

A

AG
AH
position of equilibrium

63
Q

Why can transition metals be used as catalysts

A

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
Q

What are the 2 types of catalysts

A

Homogeneous
Heterogeneous

65
Q

What are homogeneous catalysts

A

Where the catalyst is in the same phase

66
Q

What are heterogeneous catalysts

A

Catalysts in a different phase to the reactants

67
Q

What processes involve heterogeneous catalysis

A

Haber process
Contact process
Making methanol

68
Q

How do heterogeneous catalysts work

A

They absorb reactants onto the surface of catalyst, forming weak bonds
Reaction occurs
The product molecules are desorbed from surface and diffuse away

69
Q

How can the absorption of reactants increase the rate of reaction

A

Absorption concentrates the reactants, brings them closer
It may weaken bonds within the reactants
It may position the molecules in a favourable orientation

70
Q

How are catalysts used efficiently

A

Increase surface area
Spreading the catalyst onto an inert support medium - increases surface to mass ratio

71
Q

Why don’t catalysts last forever

A

The finely divided catalyst can simply come off the support medium
The catalyst becomes poisoned

72
Q

What is catalyst poisoning

A

When the surface becomes covered with unwanted impurities blocking active sites

73
Q

How is a catalyst used for the Haber process

A

Iron catalyst
N2 + 3H2 -> 2NH3
Becomes poisoned with sulphur

74
Q

What is the contact process

A

It makes sulphuric acid
The key step is:
2SO2 + O2 -> 2SO3
Catalysed by Vanadium oxide

75
Q

What are the 2 steps to catalyse the contact process

A

SO2 + V2O5 -> SO3 + V2O4
2V2O4 + O2 -> 2V2O5

76
Q

What are the reaction for making methanol

A

CH4 + H2O -> CO + 3H2
It is manufactored from sythesis gas ( CO and H2)
CO + 2H2 -> CH3OH
Cr2O3 catalyst

77
Q

How does homogeneous catalysts work

A

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
Q

What is the reaction between iodide and peroxodisulphate and how is it catalysted

A

2I- + S2O8 2- -> I2 + 2SO4 2-
Fe catalyst
S2O8 2- + 2Fe2+ -> 2SO4 2- + 2Fe3+
2Fe3+ + 2I- -> 2Fe2+ + I2

79
Q

Why is the non-catalysed reaction of iodide with peroxodisulphate so slow

A

It involves the collision of 2 negatively charged ions

80
Q

What is autocatalysis

A

It is where one of the products of a reaction is a catalyst for the reaction

81
Q

What is the reaction of ethanedioate with manganate ions

A

2MnO4- + 16H+ + 5C2O4 2- -> 2Mn2+ + 10CO2 + 8H2O

82
Q

What catalyst is there in the ethanedioate with manganate ions

A

Mn2+

83
Q

What are the equations of the catalyst reacting with the reactants in the ethanedioate with manganate ions

A

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

2MnO4- + 16H+ + 5C2O4 2- -> 2Mn2+ + 10CO2 + 8H2O

84
Q

What is the reaction between chromate ions and iron 2+

A

Cr2O7 2- + 14H+ + 6Fe2+ -> 2Cr3+ + 7H2O + 6Fe3+

85
Q

What is the reaction between manganate ions and iron 2+

A

MnO4- + 8H+ + 5Fe2+ -> Mn2+ + 4H2O + 5Fe3+

86
Q

What is the equation for frequency of light

A

speed of light/wave length

87
Q

Why in a calorimetry experiment does the container for each sample the same

A

Absorption depends on path length of light

Chemistry A Level (20 decks)

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