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Inorganic Chemistry > Transition Metals > Flashcards

Transition Metals Flashcards

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1
Q

Define a transition metal

A

A metal that can form one or more stable ions with an incomplete d-subshell

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2
Q

Why are Sc and Zn in the d-block even though they are not transition metals?

A

Their highest energy electron is in a d-subshell

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3
Q

Why are Zn and Sc not transition metals even though they are in d-block?

A

They do not form an ion with an incomplete d-subshell

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4
Q

Define a complex

A

A central metal ion surrounded by ligands

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5
Q

Define a ligand

A

A molecule or ion that forms a co-ordinate bond with a transition metal by donating a pair of electrons

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6
Q

Define a monodentate ligand

A

Molecules or ions that can donate one electron pair to the central metal ion to form one co-ordinate bond

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7
Q

Give common examples of monodentate lignads

A
  • water
  • ammonia
  • chloride
  • cyanide ion
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8
Q

define a bidentate ligand

A

Molecules or ions that can donate two electron pairs to the central metal ion to form two co-ordinate bonds

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9
Q

Give examples of bidentate ligands

A
  • diamino things (etc. 1,2-diaminoethane)
  • -dioate things (etc. ethane dioate ion (C2O42-))
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10
Q

Define a multidentate ligand

A

Molecules or ions that can donate more than two electron pairs to the central metal ionto form more than two co-ordinate bonds

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11
Q

Define co-ordinate number

A

The number of co-ordinate bonds to the central metal atom or ion

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12
Q

When is the co-ordinate number the same as the number of ligands?

A

When the ligands are monodentate

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13
Q

What is the co-ordination number of [Ni(H2NCH2CH2NH2)3]2+

A
  • H2NCH2CH2NH2 is a bidentate ligand
  • Therefore it has two co-ordinate bonds per ligand
  • So it has a co-ordiantion number of 6
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14
Q

What is the coordiantion number of [Cu(EDTA)]2+

A

6

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15
Q

What is the bond angle for an octahedral structure?

A

90

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16
Q

What is the coordination number for an octahedral structure?

A

6

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17
Q

Draw an octahedral sturcture

A
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18
Q

What is the bond angle for an tetrahedral structure?

A

109.5

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19
Q

What is the coordination number for an tetrahedral structure?

A

4

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20
Q

What is the bond angle for an square planar structure?

A

90

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21
Q

Draw a tetrahedral structure

A
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22
Q

What is the coordination number for a square planar structure?

A

4

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23
Q

Draw a square planar structure

A
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24
Q

What is the bond angle for a linear structure?

A

180

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25
Q

What is the coordination number for a linear structure?

A

2

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26
Q

Draw a linear structure

A
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27
Q

What coordination number do complexes comtaining water and/or ammonia usually have?

A

6

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28
Q

Draw [Cr(NH3)6]3+

A
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29
Q

What is normally the coordiantion number for complexes containing chloride ligands?

A

4

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30
Q

What is the difference in coordination and shape due to (Cl- compared to H2O/NH3)?

A

Cl- ions are larger to H2O and NH3

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31
Q

Draw [CuCl4]2-

A
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32
Q

What is the coordiantion number of Cu(I)

A

2

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33
Q

What is the coordiantion number of Ag(I)

A

2

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34
Q

Draw [Ag(NH3)2]+

A
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35
Q

Draw [Pt(NH3)2Cl2] (cisplatin)

A
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36
Q

Why does the shape of the molecule not change during ligand substitution reactions containing H2O and NH3

A

The ligands are similar in size so the coordination number and hence the shape doesn’t change

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37
Q

Give the equation, colour changes, coordination numbers and shapes for the reaction between aqueous cobalt (II) salts and excess ammonia

A

[Co(H2O)6]2+ + 6NH3 -> [Co(NH3)6]2+ + 6H2O

(above equation is reversible)

Colour change: pink -> pale brown

Coordination numbers: 6 -> 6

Shape: Octahedral -> octahedral

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38
Q

Give the equation, colour changes, coordination numbers and shapes for the reaction between aqueous copper (II) salts and excess ammonia

A

[Cu(H2O)6]2+ + 4NH3 -> [Cu(NH3)4(H2O)2]2+ + 4H2O

(above reaction is reversible)

Colour change: Blue -> deep blue

Coordination number: 6

Shape: octahedral

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39
Q

Give the equation, colour changes, coordination numbers and shapes for the reaction between aqueous cobalt (II) salts and concentrated HCl

A

[Co(H2O)6]2 + 4Cl- -> [CoCl4]2- + 6H2O

(above reaction is reversible)

Colour change: Pink -> blue

Coordination number: 6 -> 4

Shape: octahedral -> tetrahedral

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40
Q

Give the equation, colour changes, coordination numbers and shapes for the reaction between aqueous copper (II) salts and concentrated HCl

A

[Cu(H2O)6] + 4Cl- -> [CuCl4]2- + 6H2O

(above reaction is reversible)

Colour: Blue -> yellow

Coordination number: 6 -> 4

Shape: octahedral -> tetrahedral

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41
Q

Give the equation, colour changes, coordination numbers and shapes for the reaction between aqueous iron (III) salts and concentrated HCl

A

[Fe(H2O)6]3+ + 4Cl- -> [FeCl4]- + 6H2O

Coordination number: 6 -> 4

Shape: octahedral -> tetrahedral

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42
Q

How is a coordiate bond formed?

A

Both electrons in the shared pair come from one atom

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43
Q

What is the coordination number of the iron (II) in a heam unit (part of heamoglobin)? What is the shape?

A

Coordination number = 4

shape = square planar

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44
Q

Explain how haemoglobin forms

A

The planar haem unit is then bound to a complex protein called globin

In the body both water and oxygen and water can bond to the Fe (II) in haem as ligands

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45
Q

Explain how carbon monoxide poisoning occurs

A
  • When carbon monoxide is inhaled, the haemoglobin can substitute H2O ligands for CO
  • The bond between carbon monoxide and Iron (II) is very strond and is irreversible
  • This prevents oxygen being bonded to haemoglobin and so oxygen cannot go around the body
46
Q

In the following reaction:

[Ni(NH3)6]2+ + 3H2NCH2CH2NH2 -> [Ni(H2NCH2CH2NH2)3]2+ + 6NH3

There is a large increase in entropy, why?

This reaction is difficult to reverse ,why?

A
  • 4 moles produces 7 moles
  • The reverse process would lead to a decrease in entropy (∆G = + which is bad)
47
Q

In the following reaction:

[Cu(H2O)6]2+ + EDTA4- ->[Cu(EDTA)]2- + 6H2O

There is a large increase in entropy, why?

This reaction is irreversible, why?

A
  • 2 moles forms 7 moles, so there is a large increase in ∆S
  • In ther forward reaction ∆G is negative , so in the reverse reaction ∆G is negative which is bad
48
Q

What is the chelate effect?

A

Multidentate ligands replace monodentate ligands to form stable complexes

49
Q

Why are transition metals coloured?

A

They have an incomplete d-subshell

50
Q

How does an individual transition metal ion get its colour?

A
  • When visible light is absorbed, electrons are excited and go from the lower energy orbitals to the higher states
  • When TM ions absorb visible light corresponding to a colour, this colour is missing from the spectrum, the remaining coloures are transmitted and the complementary colour is seen
51
Q

What is Planck’s constant?

A

6.63 x10-34

52
Q

What changes will affect the colour of TM compounds?

A
  • Change in coordination number
  • Change in ligand
  • Change in oxidation state
53
Q

Why does a change in coordination number affect the colour of a TM compound?

A

The splitting in the d-orbitals is different in octahedral complexes than in tetrahedral and so when the coordination number changes from 6 to 4 the colour will also change

54
Q

Why does a change in ligand affect the colour of a TM compound?

A

Different ligands have different effects on the energies of the d-orbitals and so when the ligand changes , the size of the ∆E changes and hence the colour changes

55
Q

Why does a change in oxidation state affect the colour of a TM compound?

A

As the oxidation state of the metal increases so does the size of the energy gap ∆E. This leads to a change in colour

56
Q

What is the colour change, and cause for colour change, in the following reaction:

[Co(H2O)6]2+ + 4Cl- -> [CoCl4]2- + 6H2O

(The above reaction is reversible)

A

Colour change: pink -> blue

Cause: change in coordination number (6 -> 4)

Change of ligand (water to chloride)

57
Q

What is the colour change, and cause for colour change, in the following reaction:

[Ni(H2O)6]2+ + 6NH3 -> [Ni(NH3)6]2+ + 6H2O

(The above reaction is reversible)

A

Colour change: Green -> blue

Cause of colour change: change in ligand (water to ammonia)

58
Q

What is the colour change, and cause for colour change, in the following reaction:

[Fe(H2O)6]2+ -> [Fe(H2O)6]3+

(The above reaction is reversible)

A

Colour change: green -> yellow

Cause: change in oxidation state

59
Q

How does a colorimeter work?

A

It measures the amount of light absorbed by a solution. It gives us a measure of concentration.

60
Q

How do you use a colorimeter?

A
  • Create 4 or 5 standard solutions of known concentrations
  • select the filter of the complementary and measure the absorbance of known solutions
  • The unknowns absorbance can then be measures and its concentration found from the calibration curve
61
Q

Why must 4/5 solutions be made for colorimetry?

A

So there is a more reliable line of best fit on the calibration curve

62
Q

Why must a filter be used in colorimetry?

A

To select the complementary colour , which is the light absorbed by the sample

63
Q

Why is colorimetry a good method to find the concentration of a solution?

A

It doesn’t destroy the sample so further tests can be carried out

64
Q

Define stereoisomerism

A

Compounds with the same structural formula, but a different arrangement of atoms in space

65
Q

What shapes of TM complexes can exhibit stereoisomerism?

A

Square planar and octahedral

66
Q

When does a square complex exhibit stereoisomerism?

A

When the the complex has two different ligands

67
Q

Draw the cis and trans isomers of [Ni(NH3)2Cl2]

A
68
Q

When does an octahedral complex exhibit cis-trans isomerism?

A

When there are two different ligands: four of one and two of another

69
Q

Draw the cis-trans isomers of [Co(NH3)4Cl2]+

A
70
Q

Define optical isomers

A

non-superimposible mirror images

71
Q

When does an octahedral complex exhibit optical isomerism?

A

When it contains bidentate ligands

72
Q

Draw the optical isomers of [Ni(H2NCH2CH2NH2)3]2+

A
73
Q

Draw the optical isomers of [Co(C2O4)3]3-

A
74
Q

What isomerism do complexes with two monodentate and two bidentate ligands show?

A
  • Cis/trans (stereoisomerism)
  • optical isomerism

(only the cis isomer has optical isomerism)

75
Q

Name: VO3-

A

Vanadate (V)

76
Q

What is the oxidation state and colour of vanadium in:

VO2+

A

Oxidation state: +5

Colour: yellow

77
Q

What is the oxidation state and colour of vanadium in:

VO2+

A

State: +4

Colour: blue

78
Q

What is the oxidation state and colour of vanadium in:

V3+

A

oxidation state: 3+

Colour: green

79
Q

What is the oxidation state and colour of vanadium in:

V2+

A

State: 2+

Colour: violet

80
Q

What is the half equation for the reduction of VO2+ to VO2+

A

2H+ + 3e- + VO2+ -> VO2+ + H2O

81
Q

What is the equation for the oxidation of Zn?

A

Zn -> Zn2+ + 2e-

82
Q

What is the half equation for the reduction of VO2+ to V3+

A

e- + 2H+ + VO2+ -> V3+ + H2O

83
Q

What is the half equation for the reduction of V3+ to V2+

A

e- + V3+ -> V2+

84
Q

What is the equation for the reduction of Tollen’s reagent?

A

[Ag(NH3)2]+ + e- -> Ag + 2NH3

85
Q

What is the redox potential of an ion a measure of?

A

How easily it is reduced to a lower oxidation state

The more positive the redox potential, the more likely the ion is to be reduced (the less stable the ion will be)

86
Q

What is the ligand in standard electode potentials?

A

Standard electrode potentials are measured in aqueous solution therefore the ligands surrounding the metal ion are water molecules

87
Q

How does changing the ligand of a TM complex affect the redox potential?

A
88
Q

Write the half-equation for the reduction of dichromate (VI) in acidic conditions

A

6e- + Cr2O72- + 14H+ -> 2Cr3+ + 7H2O

(the above reaction is reversible)

89
Q

What is the equation for the reaction between manganate and Fe2+?

A

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

90
Q

What is the half equation for the reduction of manganate?

A

MnO4 + 8H+ + 5e- -> Mn2+ + 4H2O

91
Q

What is the equation for the oxidation of hydrogen peroxide?

A

H2O2 -> O2 + 2H+ + 2e-

92
Q

What is a catalyst?

A

A substance that increases the rate of reaction without being changed in chemical composition or amount

It provides an alternate route with a lower activation energy

93
Q

What quality of TM complexes allow them to act as catalysts?

A

They have variable oxidation states

94
Q

Define a heterogeneous catalyst

A

It is a catalyst in a different state/phase to the reactants

95
Q

Give an equation to show iron acting as a heterogeneous catalyst in the haber process

A

N2(g) + 3H2(g) -Fe> 2NH3(g)

Fe would be above the reversible arrow in this reaction

96
Q

Give an equation to show Vanadium (V) oxide acting as a heterogeneous catalyst in the Contact Process

A

SO2 + 1/2O2 -V2O5> SO3

V2O5 woukld be above the arrow in this reversible rraction

97
Q

Why is a thin layer of the transition metal used on a support medium?

A
  • Increases the surface area for the reaction to occur
  • Transition metals are expensive
98
Q

Explain catalyst poisoning

A
  • Heterogeneous catalysts work by adsorbing reactants to active sites on the catalyst surface
  • Impurities in the reactants may also bind to the active sites blocking the reactants
99
Q

Why does poisoning a catalyst reduce efficiency?

A

It decreases the surface area for reactants to react

100
Q

How can the poisoning of a catalys be reduced?

A

Purify the reactants

101
Q

Give the equation for step 1, step 2 and the overall equation for the contact process

A
102
Q

Define homogeneous catalyst

A

A catalyst in the same state/phase as the reactants

103
Q

In the following reaction:

S2O82-(aq) + 2I-(aq) -> 2SO42-(aq) + I2 (aq)

the reaction is very slow. Suggest a reason for this

A

The negatively charged ions will repel each other

104
Q

What is used to catalyse the reaction between S2O82- and I-?

A

Iron (II) or Iron (III)

105
Q

In the reaction between S2O82- and I-, give equations for the mechanism of the catalysis with Iron (II).

What is the formula for the intermediate species?

A

Step 1: S2O82- + Fe2+ -> 2SO42- + 2Fe3+

Step 2: 2Fe3+ + 2I- -> 2Fe2+ + I2

STEP 1 AND 2 CAN HAPPEN IN ANY ORDER

Intermediate species = Fe3+

106
Q

Why are Fe3+ ions just as effective in catalysing the reaction as Fe2+ in catalysing the reaction between S2O82- and I-

A

The steps in the reaction can occur in any order

107
Q

Define an autocatalysis

A

When the catalyst for the reaction is a reaction product

108
Q

What is the equation for the reaction between manganate (VII) ions and ethanedioate ions?

A

2MnO4-(aq) + 5C2O42-(aq) + 16H+ -> 2Mn2+(aq) + 8H2O(l) + 10CO2(g)

109
Q

What is the autocatalyst in this reaction?

2MnO4-(aq) + 5C2O42-(aq) + 16H+ -> 2Mn2+(aq) + 8H2O(l) + 10CO2(g)

A

Mn2+

110
Q

Draw a graph to show concentration of a reactant that forms an autocatalys against time

A
111
Q

Explain the shape of the graph that shows concentration of a reactant that forms an autocatalyst against time

A
  • Drops slowly at the start as the rate is slow
  • Rate increases and the concentration of the autocatalyst increases.
  • Rate decreases again as the reaction that forms the autocatalys is used up
112
Q

Give equations for step 2 and 3 of the catalysis mechanism for the reaction between Manganate (VII) ions and ethanedioate ions

A

Step 2: 4Mn2+ + MnO4- + 8H+ -> 5Mn3+ + 4H2O

Step 3: 2Mn3+ + C2O42- -> 2Mn2+ + 2CO2

Inorganic Chemistry (7 decks)

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