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Chemistry A level > Transition Metals > Flashcards

Transition Metals Flashcards

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1
Q

Where in the periodic table are transition metals found?

A

d-block

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2
Q

What are transition metals?

A

A metal that can form one or more stable ions with an incomplete d sub shell

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3
Q

Why are Scandium + Zinc not transition metals?

A

Does not form a stable ion with incomplete d sub shell
Sc3+ (only stable ion) has an empty d sub shell
Zn only forms Zn2+ and this has a full d sub shell

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4
Q

What are the Properties of Transition Metals?

A
  • Have variable oxidation states – This is because the electrons sit in 4s and 3d energy levels which are very close, hence, electrons are gained and lost using similar amounts of energy
  • Form coloured ions in solution
  • Good catalysts
  • Ability to form complex ions
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5
Q

What is a complex ion?

A

Metal ions surrounded by co-ordinately bonded ligand

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6
Q

What is a Co-ordinate bond?

A

A covalent bond in which both electrons in the shared pair come from same atom

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7
Q

What is a ligand?

A

Atom, ion or molecule that donates a pair of electrons to a central metal atom/ion. A ligand must have at least one lone pair of electrons

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8
Q

What is a monodentate ligand + Examples?

A

A ligand with one lone pair, H2O:, :NH3, :Cl-, :OH-, :CN-

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9
Q

What is a bidentate ligand?

A

A ligand with two lone pairs, Ethanedioate & Ethane-1,2-diamine

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10
Q

What is a multidentate ligand?

A

A ligand with more than two lone pairs, Haem & EDTA4-

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11
Q

How do you name complexes?

A

No. of Ligands
Name of ligands – if more than 1, order is A-Z
Name of metal ion (metal ion = ‘ate’ if its negatively charged complex for e.g Iron = ferrate. Copper = cuprate)

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12
Q

How do you calculate the Oxidation No. of Metal?

A

Total charge of complex – Sum of Ligand charges

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13
Q

What is the Co ordination Number?

A

No. of co ordinate bonds formed with Central Metal ion

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14
Q

What is the Complex shape dependent on?

A

Shape is dependent on the size of the ligands and the co-ordination number

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15
Q

Name some small ligands and how many can you fit around a central metal ion?

A

H2O:, :NH3 and you can fit 6 of them around a central metal ion

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16
Q

Name a larger ligand and how many can you fit around a central metal ion?

A

:Cl- and you can fit 4 around the central metal ion

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17
Q

Name some bidentate ligands and how many can you fit around a central metal ion?

A

Ethanedioate & Ethane-1,2-diamine and normally can only fit 3 around a central metal ion

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18
Q

What is the shape of a complex with a coordination number of 6 + Bond angles?

A

Octahedral – 90 degrees

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19
Q

What are the shapes of a complex with a coordination number of 4 + Bond angle?

A

Tetrahedral – 109.5 degrees – [CuCl4]2-

Square Planar – 90 degrees – Cisplatin – Pt[(NH3)2(Cl)2]

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20
Q

What is the shape of a complex with a coordination number of 2 + Bond angle?

A

Linear - 180 degrees – [Ag(NH3)2]+ a.k.a Tollens Reagent

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21
Q

How do you calculate Total Oxidation state of metal of complex shapes?

A

Total Oxidation state – Total Oxidation state of ligands

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22
Q

What is haemoglobin?

A

A protein found in the blood that helps to transport oxygen around the body

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23
Q

What is Haem?

A

A multidentate ligand found in haemoglobin

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24
Q

What shape is haemoglobin?

A

Octahedral

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25
Q

Explain how Haemoglobin Works?

A

Water is at the top initially, however, oxygen will substitute the water ligand in the lungs to form oxyhaemoglobin – transported around body. Later oxygen is given up and water takes its place

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26
Q

How does Carbon Monoxide poisoning work?

A

This is when the Carbon Monoxide ligands replace the water ligands. CO bonds strongly to Fe2+ and doesn’t get readily replaced by oxygen or water and this leads to headaches, dizziness; death if not treated as oxygen is unable to be transported

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27
Q

When can complex ions show optical isomers?

A

They can show optical isomerism when they are non superimposable mirror images

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28
Q

What shaped complexes with how many ligands shows optical isomers?

A

Octahedral complexes with 3 bidentate ligands

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29
Q

When can complex ions show cis-trans isomerism?

A
  • Octahedral complexes with 4 ligands of the same type and 2 ligands of a different type
  • Square planers with 2 ligands of the same type and 2 ligands of a different type
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30
Q

What is d orbital splitting?

A

This is when the d subshell split into 2 when ligands bond with the central metal ion

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31
Q

Explain d orbital splitting

A

When electrons absorb light (e.g visible), some move from ground state to the excited state (highest orbital) which creates an energy gap, ∆E

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32
Q

What does the frequencies absorbed depend on?

A

It depends on the size of ∆E. The larger the energy gap ∆E, the higher the frequency of light absorbed

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33
Q

What happens to those frequencies which are not absorbed?

A

They are reflected or transmitted

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34
Q

What colour is shown for those complexes with full or empty 3d subshells?

A

They are seen as colourless or white as no electrons can move to a higher energy level

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35
Q

What is the colour of complex ions dependent on?

A

Size of ∆E

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36
Q

What does the size of ∆E depend on?

A
  • Central metal ion and oxidation state
  • Type of Ligand
  • Coordination number
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37
Q

How do you calculate the energy absorbed when electrons jump?

A 
The formula - ∆E = hv = hc / Lambda
∆E = Energy Absorbed
h = Plancks Constant (6.63 x 10-34 Js)
v = frequency of light absorbed (Hz)
c = speed of light (3.00 x 108 m s-1)
Lambda = Wavelength of light absorbed (m)
38
Q

Give an example of a ligand substitution where the co ordination number and shape remain the same (Similar sized ligands)

A

[Co(H2O)6]2+ + 6NH3  [Co(NH3)6]2+ + 6H2O
Colour – Pink Colour – Yellow
Shape – Octahedral Shape – Octahedral

39
Q

Give an example of a ligand substitution where the coordination number and shape changes (usually when a small ligand is exchanged for a larger one)

A

[Cu(H2O)6]2+ + 4Cl-  [CuCl4]2- + 6H2O
Colour – Pale Blue Colour – Yellow
Shape – Octahedral Shape – Tetrahedral

40
Q

Give an example of a ligand substitution where the oxidation number changes

A

[Fe(H2O)6]2+  [Fe(H2O)6]3+
Colour – Pale Green Colour – Yellow
Shape – Octahedral Shape – Octahedral

41
Q

Give an example of a partial ligand substitution? ([Cu(H2O)6]2+ reacts with excess ammonia)

A

[Cu(H2O)6]2+ + 4NH3  [Cu(NH3)4(H2O)2]2+ + 4H2O
Colour – Blue Colour – Dark Blue
Shape – Octahedral Shape – Octahedral

42
Q

Give an example of a ligand substitution with different sized ligands

A

[Co(H2O)6]2+ + 4Cl-  [CoCl4]2- + 6H2O
Colour – Pink Colour – Blue
Shape – Octahedral Shape – Tetrahedral

43
Q

How does an increase in Entropy affect a complex?

A

Forms a more stable complex

44
Q

Why is the enthalpy change small in ligand substitution reactions?

A

This is because the Bonds are broken and made have similar strengths

45
Q

What happens when we substitute monodentate with bi or multidentate ligands?

A

Create a solution with more particles in it which means with have an increase in entropy; which also means a reaction is more likely to happen

46
Q

What is the Chelate effect?

A

…

47
Q

What is Vanadium?

A

A transition metal with different oxidation states and colours

48
Q

What are the 4 oxidation states and colours of Vanadium?

A

V2+ - +2 – Violet
V3+ - +3 – Green
VO2+ - +4 – Blue
VO2+ - +5 –Yellow a.k.a Vanadate(V) ion

49
Q

What type of reaction occurs when a transition metal changes oxidation state?

A

Redox Reaction

50
Q

Explain the process by which Vanadium is reduced by zinc in an acidic solution?

A

2VO2+(aq) + Zn(s) + 4H+(aq)  2VO2+(aq) + Zn2+(aq) + 2H2O(l) – Yellow  Blue
2VO2+(aq) + Zn(s) + 4H+(aq)  2V3+(aq) + Zn2+ (aq) + 2H2O(l) – Blue  Green
2V3+(aq) + Zn(s)  2V2+ (aq) + Zn2+ - Green  Violet

51
Q

What do redox potentials show?

A

How easily an ion is reduced which is the same as electrode potentials

52
Q

What type of ions are more likely to be reduced?

A

The least stable ions as they have the largest redox potentials

53
Q

What are the standard conditions for Eꝋ values?

A
  • Temp of 298K
  • Pressure at 100kPa
  • Concentrations of ions at 1 moldm-3
54
Q

Explain why there may be a difference in redox potentials to the standard values in data books?

A

This is dependent on the environment the ion is in

55
Q

What affects Redox potentials?

A

pH

Ligands

56
Q

How can Transition Metal complexes be analysed?

A

This is through Colorimetry. The colours we see are compliments of the colours absorbed by the solution

57
Q

What is colour dependent on?

A
  • Type of ligand
  • The shape of ligand
  • Oxidation state of the central metal ion
58
Q

What is a colorimeter used for?

A

It is used to measure the concentration of transition metal ions in solution by measuring the absorbance of light in a coloured sample.
What is a calibration curve/graph used for?
This will be plotting a graph of know concentrations to work out the concentration of an unknown solution

59
Q

What are the 2 types of catalysts?

A
  • Homogeneous

- Heterogeneous

60
Q

What is a heterogeneous catalyst – Give an example?

A

A catalyst that is in a different state to the reactants

The Haber Process – N2(g) + 3H2(g)  2NH3(g) – A solid Iron catalyst is used.

61
Q

What is a homogeneous catalyst – Give an example?

A

A catalyst that is in the same phase as the reactants and usually in aqueous in aqueous reactants. For example, using sulphuric acid to make an ester. Will usually form intermediate species.

62
Q

What is the Contact Process?

A

The production of Sulfuric Acid using Vanadium(V) – V2O5 Heterogeneous catalyst

  1. V2O5 + SO2  V2O4 + SO3
  2. V2O4 + 1/2O2  V2O5
63
Q

Why are Catalysts used?

A

They make products faster and can be used to lower the temperature required for a reaction. This saves energy and money and is better for the environment

64
Q

What do impurities do?

A

What do impurities do?

65
Q

What is Poisoning?

A

When an impurity blocks a site

66
Q

What are the effects of catalytic poisoning?

A

Reduces surface area of the catalyst for the reactants and this slows down the rate of reaction

67
Q

State an example of when a homogeneous catalyst is used

A

Oxidation of Iodide ions using peroxodisulfate (S2O82-) as a catalyst

68
Q

Why is a catalyst required for this reaction (peroxodisulfate)?

A

The reaction is very slow and we are trying to react 2 negatively charged ions together which repel, hence, the reaction has a high activation energy
S2O82-(aq) + 2I-(aq) –> I2(aq) + 2SO42-(aq)

69
Q

Explain the reaction of the Oxidation of Iodide ions using peroxodisulfate (S2O82-) as a catalyst

A

1) We use Fe2+ as a catalyst, we can lower the activation energy and speed up the reaction. So the first part is the reduction of peroxodisulfate
S2O82-(aq) + 2Fe2+(aq) –> 2Fe3+(aq) + 2SO42-(aq)
2) The Fe3+ intermediate produced in the first part reacts with the I- ions to produce I2 and Fe2+ is reformed
2I-(aq) + 2Fe3+(aq) –> 2Fe2+(aq) + I2(aq)

70
Q

What is autocatalysis?

A

Another form of homogeneous catalyst where the product of the reaction catalyses for the same reaction

71
Q

Give an example of autocatalysis

A

Reaction between C2O42- & MnO4-

72
Q

Explain the reaction between C2O42- & MnO4- and why is catalyst required

A

The reaction is very slow as they are negative so they repel
2MnO4-(aq) + 16H+(aq) + 5C2O42-(aq)  2Mn2+(aq) + 8H2O(l) + 10CO2(g)

1) The Mn2+ catalyses the reaction converting MnO4- into Mn3+
MnO4-(aq) + 8H+(aq) + 4Mn2+(aq)  5Mn3+(aq) + 4H2O(l)
2) The Mn3+ formed reacts with the C2O42- and Mn2+ ions are reformed
2Mn3+(aq) + C2O42-(aq)  2Mn2+(Aq) + 2CO2(g)

73
Q

What is the colour of V2+?

A

Violet

74
Q

What is the colour of V3+?

A

Green

75
Q

What is the colour of VO^2+

A

Blue

76
Q

What is the colour of VO2^+?

A

Yellow

77
Q

What is the colour of Cr+?

A

Green / violet when surrounded by 6H2O

78
Q

What is the colour of CrO72-?

A

Orange

79
Q

What is the colour of Mn2+?

A

Pale Pink

80
Q

What is the colour of MnO4-

A

Purple

81
Q

What is the colour of Fe2+

A

Pale Green

82
Q

What is the colour of Fe3+

A

Yellow

83
Q

What is the colour of Co2+

A

Pink

84
Q

What is the colour of Ni2+

A

Green

85
Q

What is the colour of Cu2+

A

Blue

86
Q

What is formed when we add a transition metal to water + give 2 examples?

A

Metal Aqua complex – Cu[(H2O)6]2+ and Fe[(H2O)6]3+

87
Q

What makes metal aqua ions acidic?

A

When reacting with water, H+ ions are produced to produce hydroxonium ions making it acidic

88
Q

What affects the acidity of a metal aqua ion complex?

A

What affects the acidity of a metal aqua ion complex?

89
Q

Why are 3+ ions more acidic than 2+ ions?

A

3+ metal ion has a higher charge density as they have a larger charge and small. This makes it more polarising than 2+ ions. They attract electrons in the O-H bond in the water more strongly which weakens the bond. Therefore, it is more likely that the H+ ions will be released which means 3+ metal ions form more acidic solutions

90
Q

2+ Metal ions with Sodium carbonate reaction?

A

[M(H2O)6]2+(aq) + CO32- (aq)  MCO3(s) + 6H2O

91
Q

3+ Metal ions with Sodium carbonate reaction?

A

2[M(H2O)6]3+(aq) + 3CO32- (aq)  2M(OH)3(H2O)3 (s) + 3CO2 (g) + 3H2O(l)

Chemistry A level (10 decks)

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