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AQA Inorganic Chemistry > Transition Metals > Flashcards

Transition Metals Flashcards

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1
Q

What is a transition metal?

A

Elements that can form 1 or more stable ions with partially filled 3d orbitals

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2
Q

Why is Sc not a transition metal?

A

Its ion Sc^3+ has an empty 3d orbital

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3
Q

What happens to electrons when forming an ion of a transition metal?

A

Electrons are removed from the 4s orbital before the 3d orbital

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4
Q

Why is Zn not a transition metal?

A

Its ion Zn^2+ has a full 3d orbital

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5
Q

What are the four main characteristics of transition metals?

A
  • Form complex ions with ligands- Form coloured compounds- Have variable oxidation states- Show catalytic activity
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6
Q

How can the four main characteristics of transition metals be explained?

A

By the fact that their atoms and ions both have partially filled 3d orbitals

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7
Q

How do transition metals accept ligand coordinate bonds?

A

Transition metal ions use vacant, hybridised 4S, 4P and 4D orbitals to accept ligand coordinate bonds

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8
Q

What are hybridised orbitals?

A

Orbitals that have been reorganised to have the same energy

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9
Q

What is a ligand?

A

A species with a lone pair

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10
Q

How is a coordinate bond formed between a transition metal and a ligand?

A

The lone pair on the ligand is accepted by vacant orbitals (both electrons come from the same atom)

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11
Q

How many lone pairs can transition metals accept?

A

4 or 6

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12
Q

What is a monodentate ligand?

A
  • 1 lone pair per ligand- 1 co-ordinate bond
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13
Q

What is a bidentate ligand?

A
  • 2 lone pairs per ligand - 2 coordinate bonds
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14
Q

What is a multidentate ligand?

A
  • Multiple lone pairs and coordinate bonds
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15
Q

What are the four shapes of complex ions?

A
  • Octahedral- Tetrahedral- Square-planar - Linear
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16
Q

What is an octahedral complex ion?

A
  • Co-ordination number = 6- 6 co-ordinate bonds- 90 degree bond angle between ligands
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17
Q

What ligands can form octahedral complex ions?

A

mono,bi and multidentate ligands

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18
Q

What is a tetrahedral complex ion?

A
  • Co-ordination number = 4- 4 co-ordinate bonds- 109.5 degree bond angle between ligands
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19
Q

What ligands form tetrahedral complex ions?

A

Large and charged ions which repel one another

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20
Q

What is a square planar complex ion?

A
  • Co-ordination number = 4- 4 co-ordinate bonds- 90 degree bond angle between ligands
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21
Q

What is an example of a square planar complex ion?

A

Cisplatin

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22
Q

What is a linear complex ion?

A
  • Co-ordination number = 2- 2 co-ordinate bonds- 180 degree bond angle between ligands
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23
Q

What is an example of a linear complex ion?

A

Tollens reagent

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24
Q

<p>What is the complex ion formed between copper and water?</p>

A

<p>[Cu(H2O)6]2+</p>

<p></p>

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25
Q

<p>What state is[Cu(H2O)6]2+found in and why?</p>

A

<p>Aqueous because it has a charge</p>

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26
Q

<p>What is the colour of the[Cu(H2O)6]2+solution?</p>

A

<p>Light blue</p>

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27
Q

<p>What happens if excess Cl is added to[Cu(H2O)6]2+and how is Cl often added to the solution?</p>

A

<p>Cl is often added as HCl.</p>

<p>When added to[Cu(H2O)6]2+ Cl-causes ligand exchange to form [Cu(Cl)4]2-(aq) + 6H2O in a reversible reaction.</p>

<p>Because the Cl- ligandis large and charged, the co-ordination number is changed from 6 to 4 because of repulsion. This means the bond agle goes from 90 degrees to 109.5 degrees</p>

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28
Q

<p>What is the colour of[Cu(Cl)4]2-(aq)?</p>

A

<p>Solution is lime green</p>

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29
Q

<p>What happens to [Cu(H2O)6]2+if 2NH3(aq) are added?</p>

A

<p>The ligand NH3acts as a base and accepts 2 H+from 2 of the H2O ligands forming 2OH-ligands.</p>

<p>[Cu(H2O)6]2+ (aq)+ 2NH3(aq)⇒ [Cu(OH-)2(H2O)<span>4</span>] (s) + 2NH4+(aq)</p>

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30
Q

<p>What colour is[Cu(OH-)2(H2O)4] (s)</p>

A

<p>A light blue precipitate</p>

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31
Q

<p>What happens if excess ammonia (NH3) is added to either [Cu(H2O)6]2+ (aq) or [Cu(OH-)2(H2O)4] (s)</p>

A

<p>A royal blue solution of [Cu(H2O)2(NH3)4]2+(aq) and 4H2O is formed by ligand exchange</p>

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32
Q

<p>How can you go from [Cu(H2O)2(NH3)4]2+(aq)to [Cu(H2O)6]2+(aq)</p>

A

<p>Add excess water</p>

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33
Q

<p>What is the shape of [Cu(H2O)6]2+(aq)?</p>

A

<p>Octahedral</p>

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34
Q

<p>What is the shape of [Cu(H2O)2(NH3)4]2+(aq)?</p>

A

<p>Octahedral</p>

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35
Q

<p>What is the shape of [Cu(H2O)4(OH)2](s)?</p>

A

<p>Octahedral</p>

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36
Q

<p>What is the shape of [Cu(Cl)4]2- (aq)</p>

A

<p>Tetrahedral</p>

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37
Q

<p>What is [Co(H2O)6]2+(aq)?</p>

A

<p>An octohedral complex ion that forms a pink solution</p>

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38
Q

<p>What is [CoCl4]2-(aq)?</p>

A

<p>A tetrahedral complex ion that appears as a dark blue solution</p>

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39
Q

<p>What is [Co(NH3)6]2+(aq)?</p>

A

<p>A octahedral complex ion that appears as a light brown solution</p>

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40
Q

<p>What is [Co(OH)2(H2O)4] (s)?</p>

A

<p>An octahedral complex ion that appears as a green precipitate</p>

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41
Q

<p>What forms when excess Cl is added to [Co(H2O)6]2+(aq),how is the Cl added and what happens to the shape of the complex ion?</p>

A

<p>Cl is added in concHCl and a dark blue solution of [CoCl4]2-+ 6H2O is formed by ligand exchange in a reversible reaction (Add excess H2O to reverse). Due to Cl being large and charged shape changes from octahedral to tetrahedral because of repulsion, therefore coordination number is now 4</p>

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42
Q

<p>What happens when excess ammonia is added to [Co(H2O)6]2+?</p>

A

<p>A light brown solution of [Co(NH3)6]2+(aq) + 6H2O (l) is formed by ligand exhange in a reversible reaction (add excess H2O to reverse)</p>

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43
Q

<p>What happens when 2NH3are added to to [Co(H2O)6]2+(aq)?</p>

A

<p>A green precipitate of [Co(OH)2(H2O)4] (s) and 2NH4+is formed because NH3acts as a base and accepts 2 H+from 2 of the H2O ligands leaving two of them as OH and forming two ammonium ions</p>

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44
Q

<p>What happens to[Co(OH)2(H2O)4] (s) When excess ammonia (aq) is added?</p>

A

<p>A light brown solution of [Co(NH3)6]2+(aq) + 6H2O (l) forms</p>

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45
Q

<p>What is [Fe(H2O)6]3+?</p>

A

<p>A yellow orange solution of a octahedral complex ion</p>

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46
Q

<p>What is [FeCl4]-?</p>

A

<p>A yellow/brown solution of a tetrahedral complex ion</p>

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47
Q

<p>What is [Fe(OH)3(H2O)3]?</p>

A

<p>An orange brown precipitate of an octahedral complex</p>

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48
Q

<p>What happens if you add Cl to [Fe(H2O)6]3+(aq)?</p>

A

<p>Adding HCl causes ligand exchange to take place in a reversible reaction to form [FeCl4]-(aq) + 6H2O (l). Due to the Cl-ligand being large and charged complex shape is changed from octahedral to tetrahedral due to repulsion. Bond angle is now 109.5.</p>

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49
Q

<p>What happens if you add 3NH3to [Fe(H2O)6]3+(aq)?</p>

A

<p>The NH3ligand acts as a base and accepts 3 H+ions from 3 H2O ligands to form 3 OH-ligands. This creates a brown precipitate of [Fe(OH)3(H2O)3] (s) + 3NH4+(aq)</p>

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50
Q

<p>What happens if you add excessNH3to [Fe(H2O)6]3+(aq)?</p>

A

<p>Nothing,[Fe(H2O)3(OH)3]will not redisolve with excess NH3and ligand exchange will not take place</p>

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51
Q

What is a bidentate ligand?

A

A molecule that contains two atoms that can coordinately bond to a central ion in a complex using lone pairs

52
Q

What are two examples of bidentate ligands?

A
  • Ethan-1,2-diamine - Ethanedioate ion
53
Q

What shaped complex ions do bidentate ligands form with transition metals?

A

Octahedral so bidentate ligands lie at 90 degrees to each other

54
Q

What does the chelate effect mean in terms of ligand substitution?

A

Bidentate ligands will always be substituted in place of a monodentate ligand

55
Q

What is a multidentate ligand?

A

A molecule than contains multiple atoms that can co-ordinately bond to a central ion in a complex

56
Q

What are two examples of multidentate ligands?

A

EDTA and haemoglobin

57
Q

What is EDTA?

A
  • EthyleneDiamineTetraAcetic Acid- Can form 6 coordinate bonds- 4- charge
58
Q

What does haemoglobin do?

A

Carries oxygen molecules around the body

59
Q

What is the lower ligand of haemoglobin when deoxygenated?

A

H2O

60
Q

What is the lower ligand of haemoglobin when oxygenated?

A

O2

61
Q

What happens to haemoglobin in the presence of carbon monoxide?

A

Carbon monoxide coordinately bonds to haemoglobin in the same place that oxygen would. This bond is permanent and ligand exchange cannot take place

62
Q

What is the chelate effect?

A

Bidentate and mutidentate ligands readily substitute/exchange in place of mono dentate ligands, creating a more stable complex

63
Q

How can the chelate effect be explained

A
  • Moles of product are higher than moles of reactant (increase in entropy), delta S is positive (reactions tend towards entropy increase - Enthalpy change (delta H) is negligible because the same number of coordinate bonds are broken and formed - delta G = delta H - (T x delta S), delta G will always be negative because of the negligible delta H, positive temp and positive delta S- Exchange always happens readily as it is feasible at any temperature
64
Q

What types of isomerism can monodentate complexes show?

A

Cis-trans

65
Q

When does cis-trans isomerism show in octahedral complexes?

A

When you have a 4:2 split in ligand type

66
Q

What are cis isomers?

A

Same side

67
Q

What are trans isomers?

A

Opposite side

68
Q

When does cis-trans isomerism show in square planar complexes?

A

When you have a 2:2 split in ligand type

69
Q

What is an example of a square planar complex that shows cis-trans isomerism?

A

Cisplatin and transplatin

70
Q

What isomerism can bidentate complexes show?

A

Optical isomerism

71
Q

Which bidentate complexes can show optical isomerism?

A

Any bidentate complex

72
Q

What are three facts about optical isomers?

A
  • non superimposable- will rotate plane polarised light- it is possible to haver a racemic mixture (equimolar concentrations of both)
73
Q

Why are transition metal complexes coloured?

A
  • They have partially filled d orbitals- When ligands coordinately bond they cause d orbitals to split from 1 energy level to 2- Frequencies of visible light cause 1 or 2 electrons to be promoted from the lower d orbitals (ground state) to a higher d orbital (excited state)- Energy difference between these orbitals is delta E- Delta E varies so the frequencies of visible light that are not absorbed are reflected
74
Q

What is delta E affected by?

A
  • Oxidation state of the transition metal ion- Type of ligand- Coordination number
75
Q

What size delta E would you expect from a blue solution?

A

Blue has a high frequency, if blue is reflected then a lower wavelength is absorbed therefore the complex would have a lower delta E

76
Q

The greater the delta E…

A

The greater the frequency of light absorbed

77
Q

Name the colours from shortest to longest wavelength of light

A

ROYGBIV

78
Q

How do you calculate delta E?

A

hf

79
Q

What is delta E?

A

The difference in energy between split orbitals

80
Q

What is h?

A

Planks constant (6.63 x 10^-34)

81
Q

What if f?

A

Frequency (Hz)

82
Q

How can you calculate frequency?

A

Speed of light / wavelength (m)

83
Q

How do you convert from atoms to moles?

A

x Avogadros constant

84
Q

How do you convert from nanometers to meters?

A

x 10^-9

85
Q

How do you convert from joules to Kj?

A

/1000

86
Q

What can transitional metals have?

A

Variable oxidation states

87
Q

Why can transition metals have variable oxidation states?

A

4S electrons are lost before 3D electrons when ions form, this allows them to have a number of stable electronic configurations within the partially filled d orbitals

88
Q

What trend do T.Ms follow from Ti to Mn?

A

Increase in number of stable oxidation states

89
Q

What trend do T.Ms follow from Cu to Mn?

A

Increase in number of stable oxidation states

90
Q

What do T.Ms do when they have a low oxidation state?

A

Act as reducing agents and tend to be oxidised to higher oxidation states

91
Q

What do T.Ms do when they have a high oxidation state?

A

Act as oxidising agents and tend too be reduced to a lower oxidation state

92
Q

What two factors affect the potential for a transition metal to be reduced from a higher to a lower oxidation state?

A

pH and ligand type

93
Q

What is more likely to happen to transition metal ions in acidic conditions?

A

Reduced

94
Q

What is more likely to happen to transition metal ions in alkaline conditions?

A

Oxidised

95
Q

How does ligand type affect the REDOX potential of a T.M?

A

Some ligands for stronger coordinate bonds than others, the stronger the coordinate bond (enthalpy) the less likely the T.M is to be oxidised/reduced

96
Q

How can vanadium be reduced by Zn(s)?

A

V can be reduced through 3 steps by Zn, from VO2^+(aq) to V^2+(aq) in acidic conditions

97
Q

What are the stages of the reduction of vanadium by zinc?

A

1 - VO2^+(aq) to VO^2+(aq)2 - VO^2+(aq) to V^3+(aq)3 - V^3+(aq) to V^2+(aq)

98
Q

What is the colour and oxidation state of V in VO2^+(aq)?

A

yellow and +5

99
Q

What is the colour and oxidation state of V in VO^2+(aq)?

A

blue and +4

100
Q

What is the colour and oxidation state of V^3+(aq)?

A

green and +3

101
Q

What is the colour and oxidation state of V^2+(aq)?

A

violet and +2

102
Q

What is oxidised?

A

Fe^2+ to Fe^3+

103
Q

What is reduced?

A

Mn from +7(MnO4^-) to +2(Mn^2+)

104
Q

What colour is MnO4^-?

A

Purple

105
Q

What colour is Mn^2+?

A

Colourless

106
Q

What are the conditions and how are the conditions achieved?

A

Acidic, added dilute H2SO4 to supply the H+ ions

107
Q

What is the ratio of Fe^2+ to MnO4^-?

A

5:1

108
Q

How do you carry out the titration?

A

1 - Fill burette with MnO4^- of a known conc2 - add a known volume of Fe^2+ (aq) (250cm^3)3 - Add MnO4^-, colour changed from purple to colourless as Fe^2+ is oxidised and MnO4^- is reduced4 - When Fe ^2+ runs out, colour change stops5 - When solution in flask stays purple the titration is done6 - nFe^2+ = nMnO4^- x 5

109
Q

What is oxidised?

A

C in C2O4^2-

110
Q

What is reduced?

A

Mn in MnO4^-

111
Q

What is the colour change?

A

Purple to colourless

112
Q

What is the mole ratio?

A

5C2O4^2- : 2MnO4^-

113
Q

What goes in the flask?

A

Known volume of C2O4^2-

114
Q

What goes in the burette?

A

Known conc and volume of MnO4^-

115
Q

What is the reaction process?

A
  • 2MnO4^- converted to Mn^2+ by C2O4^2– Purple to colourless
116
Q

What is the mole calc?

A

nC2O4^2- = nMnO4^- x 2.5

117
Q

What phase is the catalyst in?

A

A different phase to the reactants

118
Q

What state is the catalyst usually?

A

A solid T.M in a (aq) or (g) reaction

119
Q

What are two examples of heterogeneous catalysts?

A

Fe (s) in the Haber process and V2O5 (s) in the contact

120
Q

Why are T.Ms used as heterogeneous catalysts?

A

Have multiple stable oxidation states

121
Q

How can you increase the efficiency of a heterogeneous catalyst?

A
  • Increase the surface area (powder)- Spread the catalyst over a support medium to increase efficiency (less catalyst over a bigger area)
122
Q

Why does efficiency decrease over time?

A

“Poisoning” occurs due to impurities sticking to the surface and blocking the interaction between the catalyst and the reactants

123
Q

What are homogeneous catalysts?

A

Catalysts that exist in the same phase as the reactants

124
Q

What do catalysts do?

A

Provide a reaction pathway with lower activation energy from forming an intermediate in a two step reaction

125
Q

When does autocatalysis occur?

A

When one of the products of a reaction acts as a catalyst for the reaction

126
Q

Explain the graph of a reaction where autocatalysis is occuring

A
  • Very slow rate when not a lot of product is produced- As product increases so does the rate (rapidly)- Reaction slows as the conc of reaction approaches 0
127
Q

Why can autocatalysis take place?

A

T.Ms have variable stable oxidation states

AQA Inorganic Chemistry (4 decks)

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