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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

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

Aqueous because it has a charge

26

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

Light blue

27

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

Cl is often added as HCl.

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

Because the Cl- ligand is 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

28

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

Solution is lime green

29

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

The ligand NH3 acts as a base and accepts 2 H+ from 2 of the H2O ligands forming 2OH- ligands.

[Cu(H2O)6]2+ (aq) + 2NH3 (aq) ⇒ [Cu(OH-)2(H2O)4] (s) + 2NH4+ (aq)

30

What colour is [Cu(OH-)2(H2O)4] (s)

A light blue precipitate 

31

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

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

32

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

Add excess water

33

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

Octahedral

34

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

Octahedral

35

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

Octahedral 

36

What is the shape of [Cu(Cl)4]2- (aq)

Tetrahedral

37

What is [Co(H2O)6]2+(aq)?

An octohedral complex ion that forms a pink solution

38

What is [CoCl4]2- (aq)?

A tetrahedral complex ion that appears as a dark blue solution

39

What is [Co(NH3)6]2+ (aq)?

A octahedral complex ion that appears as a light brown solution

40

What is [Co(OH)2(H2O)4] (s)?

An octahedral complex ion that appears as a green precipitate 

41

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?

Cl is added in conc HCl 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

42

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

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) 

43

What happens when 2NH3 are added to to [Co(H2O)6]2+(aq) ?

A green precipitate of [Co(OH)2(H2O)4] (s) and 2NH4+ is formed because NH3 acts as a base and accepts 2 H+ from 2 of the H2O ligands leaving two of them as OH and forming two ammonium ions

44

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

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

45

What is [Fe(H2O)6]3+?

A yellow orange solution of a octahedral complex ion

46

What is [FeCl4]- ?

A yellow/brown solution of a tetrahedral complex ion

47

What is [Fe(OH)3(H2O)3]?

An orange brown precipitate of an octahedral complex

48

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

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.

49

What happens if you add 3NH3 to [Fe(H2O)6]3+ (aq)?

The NH3 ligand 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) 

50

What happens if you add excess NH3 to [Fe(H2O)6]3+ (aq)?

Nothing, [Fe(H2O)3(OH)3] will not redisolve with excess NH3 and ligand exchange will not take place

51
What is a bidentate ligand?
A molecule that contains two atoms that can coordinately bond to a central ion in a complex using lone pairs
52
What are two examples of bidentate ligands?
- Ethan-1,2-diamine - Ethanedioate ion
53
What shaped complex ions do bidentate ligands form with transition metals?
Octahedral so bidentate ligands lie at 90 degrees to each other
54
What does the chelate effect mean in terms of ligand substitution?
Bidentate ligands will always be substituted in place of a monodentate ligand
55
What is a multidentate ligand?
A molecule than contains multiple atoms that can co-ordinately bond to a central ion in a complex
56
What are two examples of multidentate ligands?
EDTA and haemoglobin
57
What is EDTA?
- EthyleneDiamineTetraAcetic Acid- Can form 6 coordinate bonds- 4- charge
58
What does haemoglobin do?
Carries oxygen molecules around the body
59
What is the lower ligand of haemoglobin when deoxygenated?
H2O
60
What is the lower ligand of haemoglobin when oxygenated?
O2
61
What happens to haemoglobin in the presence of carbon monoxide?
Carbon monoxide coordinately bonds to haemoglobin in the same place that oxygen would. This bond is permanent and ligand exchange cannot take place
62
What is the chelate effect?
Bidentate and mutidentate ligands readily substitute/exchange in place of mono dentate ligands, creating a more stable complex
63
How can the chelate effect be explained
- 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
What types of isomerism can monodentate complexes show?
Cis-trans
65
When does cis-trans isomerism show in octahedral complexes?
When you have a 4:2 split in ligand type
66
What are cis isomers?
Same side
67
What are trans isomers?
Opposite side
68
When does cis-trans isomerism show in square planar complexes?
When you have a 2:2 split in ligand type
69
What is an example of a square planar complex that shows cis-trans isomerism?
Cisplatin and transplatin
70
What isomerism can bidentate complexes show?
Optical isomerism
71
Which bidentate complexes can show optical isomerism?
Any bidentate complex
72
What are three facts about optical isomers?
- non superimposable- will rotate plane polarised light- it is possible to haver a racemic mixture (equimolar concentrations of both)
73
Why are transition metal complexes coloured?
- 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
What is delta E affected by?
- Oxidation state of the transition metal ion- Type of ligand- Coordination number
75
What size delta E would you expect from a blue solution?
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
The greater the delta E...
The greater the frequency of light absorbed
77
Name the colours from shortest to longest wavelength of light
ROYGBIV
78
How do you calculate delta E?
hf
79
What is delta E?
The difference in energy between split orbitals
80
What is h?
Planks constant (6.63 x 10^-34)
81
What if f?
Frequency (Hz)
82
How can you calculate frequency?
Speed of light / wavelength (m)
83
How do you convert from atoms to moles?
x Avogadros constant
84
How do you convert from nanometers to meters?
x 10^-9
85
How do you convert from joules to Kj?
/1000
86
What can transitional metals have?
Variable oxidation states
87
Why can transition metals have variable oxidation states?
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
What trend do T.Ms follow from Ti to Mn?
Increase in number of stable oxidation states
89
What trend do T.Ms follow from Cu to Mn?
Increase in number of stable oxidation states
90
What do T.Ms do when they have a low oxidation state?
Act as reducing agents and tend to be oxidised to higher oxidation states
91
What do T.Ms do when they have a high oxidation state?
Act as oxidising agents and tend too be reduced to a lower oxidation state
92
What two factors affect the potential for a transition metal to be reduced from a higher to a lower oxidation state?
pH and ligand type
93
What is more likely to happen to transition metal ions in acidic conditions?
Reduced
94
What is more likely to happen to transition metal ions in alkaline conditions?
Oxidised
95
How does ligand type affect the REDOX potential of a T.M?
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
How can vanadium be reduced by Zn(s)?
V can be reduced through 3 steps by Zn, from VO2^+(aq) to V^2+(aq) in acidic conditions
97
What are the stages of the reduction of vanadium by zinc?
1 - VO2^+(aq) to VO^2+(aq)2 - VO^2+(aq) to V^3+(aq)3 - V^3+(aq) to V^2+(aq)
98
What is the colour and oxidation state of V in VO2^+(aq)?
yellow and +5
99
What is the colour and oxidation state of V in VO^2+(aq)?
blue and +4
100
What is the colour and oxidation state of V^3+(aq)?
green and +3
101
What is the colour and oxidation state of V^2+(aq)?
violet and +2
102
What is oxidised?
Fe^2+ to Fe^3+
103
What is reduced?
Mn from +7(MnO4^-) to +2(Mn^2+)
104
What colour is MnO4^-?
Purple
105
What colour is Mn^2+?
Colourless
106
What are the conditions and how are the conditions achieved?
Acidic, added dilute H2SO4 to supply the H+ ions
107
What is the ratio of Fe^2+ to MnO4^-?
5:1
108
How do you carry out the titration?
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
What is oxidised?
C in C2O4^2-
110
What is reduced?
Mn in MnO4^-
111
What is the colour change?
Purple to colourless
112
What is the mole ratio?
5C2O4^2- : 2MnO4^-
113
What goes in the flask?
Known volume of C2O4^2-
114
What goes in the burette?
Known conc and volume of MnO4^-
115
What is the reaction process?
- 2MnO4^- converted to Mn^2+ by C2O4^2-- Purple to colourless
116
What is the mole calc?
nC2O4^2- = nMnO4^- x 2.5
117
What phase is the catalyst in?
A different phase to the reactants
118
What state is the catalyst usually?
A solid T.M in a (aq) or (g) reaction
119
What are two examples of heterogeneous catalysts?
Fe (s) in the Haber process and V2O5 (s) in the contact
120
Why are T.Ms used as heterogeneous catalysts?
Have multiple stable oxidation states
121
How can you increase the efficiency of a heterogeneous catalyst?
- Increase the surface area (powder)- Spread the catalyst over a support medium to increase efficiency (less catalyst over a bigger area)
122
Why does efficiency decrease over time?
"Poisoning" occurs due to impurities sticking to the surface and blocking the interaction between the catalyst and the reactants
123
What are homogeneous catalysts?
Catalysts that exist in the same phase as the reactants
124
What do catalysts do?
Provide a reaction pathway with lower activation energy from forming an intermediate in a two step reaction
125
When does autocatalysis occur?
When one of the products of a reaction acts as a catalyst for the reaction
126
Explain the graph of a reaction where autocatalysis is occuring
- 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
Why can autocatalysis take place?
T.Ms have variable stable oxidation states

AQA Inorganic Chemistry (4 decks)

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