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Chemistry (Inorganic) > Transition metals > Flashcards

Transition metals Flashcards

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1
Q

What is a transition metal

A

A d- block element that can form at least one stable ion with an incomplete d-subshell, or exists as an atom which has an incomplete d-subshell

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2
Q

Why do Cr and Cu have electron configurations (Ar)3d5,4s1 and (Ar)3d10,4s1 respectively

A

An e- from the 4s orbital moving into the 3d orbital to create a more stable half full or full 3d subshell

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3
Q

Why is Zn not a transition metal

A

Forms only 1 stable ion: Zn2+ which has a full-subshell

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4
Q

Give 4 properties of transition metals

A

Variable oxidation states
Coloured ions in solution
Good catalysts
Complex formation

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5
Q

Why do transition metals have variable oxidation states

A

Electrons sit in the 4s and 3d subshells which are very close, therefore electrons are gained and lost using a similar amount of energy when they form ions

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6
Q

What is the Pneumonic to remember the colours of vanadium

A

You (VO₂⁺)
Better (VO²⁺)
Get (V³⁺)
Vanadium (V²⁺)

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7
Q

What colour is VO₂⁺(aq)

A

Yellow

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8
Q

What colour is VO²⁺(aq)

A

Blue

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9
Q

What colour is V³⁺(aq)

A

Green

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10
Q

What colour is V²⁺ (aq)

A

Violet

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11
Q

What colour is Cr³⁺(aq)

A

Green/Violet

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12
Q

When is Cr³⁺(aq) violet

A

When surrounded by water ligands, however commonly substituted with other molecules and so usually green

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13
Q

What colour is Cr₂O₇⁻(aq)

A

Orange

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14
Q

What colour is Mn²⁺(aq)

A

Pale pink

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15
Q

What colour is MnO₄⁻(aq)

A

Purple

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16
Q

What colour is Fe²⁺(aq)

A

Pale green

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17
Q

What colour is Fe³⁺(aq)

A

Orange (rust)

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18
Q

What colour is CO²⁺(aq)

A

Pink

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19
Q

What colour is Ni²⁺(aq)

A

Green

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20
Q

What colour is Cu²⁺(aq)

A

Blue

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21
Q

What colour are Zn²⁺(aq) and Sc³⁺(aq)

A

Colourless

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22
Q

What is a complex ion

A

A central transition metal ion is surrounded by ligands bonded by dative covalent bonds

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23
Q

What is a ligand

A

A molecule/ion that forms a covalent bond with a central metal atom by donating a pair of e-

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24
Q

What is a monodentate ligand

A

Ligands which only donate 1 pair of e- (to a transition metal ion) from one atom on the molecule/ion, forming 1 coordinate bond

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25
Q

Give 3 examples of monodentate ligands

A

:H2O
:NH3
:Cl-

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26
Q

What is a bidentate ligand

A

Ligands which donate 2 pairs of e- (to a transition metal ion) from 2 atoms on the molecule/ion, forming 2 coordinate bonds

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27
Q

Draw the structure of ethanedioate

A

Double bond C=C
Two C–:O- single bonds (bonded to central C’s)
Two O=O bonds (bonded to central C’s)

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28
Q

Draw the structure of
Ethane-1,2-diamine

A

Two single bonded CH2
Two single bonded :NH2 bonded to central C from CH2

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29
Q

What is a multidentate ligand

A

Ligands which donate 2 or more pairs of e- (to a transition metal ion) from 2 or more atoms on the molecule/ion, forming 2 or more coordinate bonds

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30
Q

Give 2 examples of Multidentate ligands

A

EDTA⁴⁻
Haem

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31
Q

How many coordinate bonds does EDTA⁴⁻ form

A

6

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32
Q

How many coordinate bonds does Haem form

A

4

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33
Q

What is the shape of a complex dependent on

A

The size of ligands bonded
Coordination number

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34
Q

What is a coordination number

A

The number of coordinate bonds in a complex (Not number of ligands)

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35
Q

How many :NH3 and H2O: ligands can fit around a central metal ion

A

6

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36
Q

How many Cl- ligands can fit around a central metal ion

A

4

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37
Q

Give an example of 2 ligands where only 3 of them can fit around a central metal ion

A

Ethanedioate
Ethane-1,2-diamine

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38
Q

What shape do complexes with a coordination number of 6 form

A

Octahedral

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39
Q

What is bond angle in an octahedral structure

A

All angles 90 degrees

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40
Q

What shape do complexes with a coordination number of 4 form

A

Tetrahedral and square planar shapes

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41
Q

Draw the structure of cis-platin

A
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42
Q

What is cis-platin

A

An anti cancer drug

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43
Q

What is the bond angle in a tetrahedral structure

A

109.5 degrees

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44
Q

What is the bond angle in a square planar structure

A

90 degrees

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45
Q

How does cis platin work

A

Kills cancer by preventing cell division

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46
Q

What is a risk with cis-platin

A

Also kills healthy cells

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47
Q

How are risks associated with cis-platin minimised

A

By using small amounts/in short bursts

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48
Q

What shape do complexes with a coordination number of 2 form

A

Linear shape

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49
Q

Give an example of a complex with a linear shape

A

Tollens reagent

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50
Q

Draw the structure of tollens reagent

A
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51
Q

What is the bond angle in a linear complex

A

180 degrees

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52
Q

What is tollens reagent used for

A

To distinguish between aldehydes and ketones

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53
Q

How do we calculate the oxidation state of the central metal ion in a complex

A

Oxidation state of metal = Total oxidation state (complex charge) - total oxidation state of ligands

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54
Q

What shape is haemoglobin

A

Octahedral

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55
Q

State where each of the coordinate bonds in haemoglobin come from

A

4 Nitrogen from one multidentate ligand: Haem
1 From globin protein
1 from either oxygen/water molecule

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56
Q

Explain how haemoglobin transports oxygen around the body

A

Oxygen substitutes water ligand in the lungs (where there is a high (O2) ) forming oxyhaemoglobin
This then gives up oxygen to organs and is substituted by water formed from respiration in muscle cells

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57
Q

What is CO

A

Carbon monoxide
A poisonous gas that causes headaches, unconsciousness and death

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58
Q

What colour is CO

A

Colourless and odourless

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59
Q

What happens when CO is inhaled

A

CO replaces the H2O/O2 ligand on haemoglobin

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60
Q

Why is CO dangerous when bonded to haemoglobin

A

It bonds strongly
Therefore not readily replaced by O2/H2O and so O2 cant be transported which leads to oxygen starvation

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61
Q

Why is CO not readily replaced by H2O/O2 in haemoglobin

A

CO has 210 times greater affinity to haemoglobin than oxygen

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62
Q

What does CO poisoning lead to

A

Oxygen starvation

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63
Q

What is the condition for a complex to display optical isomerism

A

When complexes are non-superimposable mirror images

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64
Q

What is the most likely case for optical isomerism

A

In octahedral complexes with 3 bidentate ligands

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65
Q

What is the most likely case for Cis-Trans isomerism

A

Octahedral complexes with 4 ligands of the same type and 2 ligands of a different type
Square planar complexes with 2 ligands of the same type and 2 ligands of a different type

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66
Q

When do we see Trans isomers

A

When the 2 ligands of the same type which are opposite each other

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67
Q

When do we see Cis isomers

A

When the 2 ligands of the same type which are adjacent to each other

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68
Q

Give an example of a molecule which displays Cis-Trans isomerism

A

Cis-Trans platin

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69
Q

What is the difference between cis-trans platin

A

Cis-Platin is an anti cancer drug
Trans-Platin is not

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70
Q

When does d-subshell splitting of a metal ion occur

A

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

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71
Q

Why do we get d-subshell splitting of a metal ion when ligands bond

A

Some orbitals gain energy and therefore an energy gap is created

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72
Q

What is the ground state of electrons

A

The state electrons are in when ligands are attached (without light the input of light energy)

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73
Q

How can electrons move from the ground state to an excited state

A

By absorbing light energy

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74
Q

What is the an excited state of electrons

A

The state electrons are in when ligands are attached after the absorbance of light energy

75
Q

What is the must exist about relationship between light energy and ∆E in order for an electron to be excited

A

Energy from light energy must equal ∆E in order for an electron to be excited

76
Q

What does ∆E correspond to when an electron is excited

A

∆E will correspond to one of the wavelengths of light

77
Q

Why cant Sc go from the ground state to an excited state

A

Sc ions have empty d-subshells

78
Q

Why cant Zn go from the ground state to an excited state

A

Zn ions have full d-subshells

79
Q

What 3 things is the magnitude of ∆E dependent on

A

Central metal ion and its oxidation state
Type of ligand bonded
Coordination number

80
Q

What is the equation for calculating energy absorbed by electrons from the ground state to an excited state

A

∆E = hv = hc/λ

81
Q

What does ∆E represent in the equation ∆E = hv = hc/λ and what is its units

A

Change in energy
(J)

82
Q

What does h represent in the equation ∆E = hv = hc/λ

A

Planck’s constant

83
Q

What does v represent in the equation ∆E = hv = hc/λ and what is its units

A

Frequency of light absorbed
(Hz)

84
Q

What does c represent in the equation ∆E = hv = hc/λ

A

Speed of light

85
Q

What does λ represent in the equation ∆E = hv = hc/λ and what is its units

A

Wavelength of light absorbed
(m)

86
Q

What does the frequency of light absorbed by transition metal complexes depend on

A

The size of ∆E

87
Q

When white light hits a transition metal solution, only 1 frequency is absorbed. Write the colours of visible light in order of increasing frequency

A

R O Y G B I V
–Increasing frequency—>

88
Q

What does a larger ∆E mean about the frequency of light absorbed by e-

A

Larger ∆E means a higher frequency of light is absorbed

89
Q

What happens to frequencies of light which aren’t absorbed by an e- when excited

A

Either reflected transmitted

90
Q

What creates a complementary colour (the colour we see observe metal complexes)

A

A combination of the frequencies of visible light which are reflected or transmitted when an e- is excited

91
Q

What does a colour of a complex ion depend on

A

The size of ∆E
Coordination number
Change of ligand

92
Q

Give the equation for a ligand substitution where coordination number and shape stay the same. State the colour and shape of the complex in reactants and products

A

(Co(H2O)6)²⁺(aq) + 6NH3(aq) –> (Co(NH3)6)²⁺(aq) + 6H2O(l)
(Co(H2O)6)²⁺(aq) - Pink, Octahedral
(Co(NH3)6)²⁺(aq) - Straw, Octahedral

93
Q

Give the equation for a ligand substitution where both coordination number and shape change. State the colour and shape of the complex in reactants and products

A

(Cu(H2O)6)²⁺(aq) + 4Cl-(aq) —> (Cu(Cl4))²⁻(aq) + 6H2O(l)
(Cu(H2O)6)²⁺(aq) - Pale blue, Octahedral
(Cu(Cl4))²⁻(aq) - Yellow, Tetrahedral

94
Q

When is ligand substitution where both coordination number and shape change most likely

A

When a smaller ligand is substituted by a larger ligand

95
Q

Give the equation for a ligand substitution where oxidation state changes, but coordination number and shape stay the same. State the colour and shape of the complex in reactants and products

A

(Fe(H2O)6)²⁺(aq) —> (Fe(H2O)6)³⁺(aq)
(Fe(H2O)6)²⁺(aq) - Pale green - Octahedral
(Fe(H2O)6)³⁺(aq) - Yellow - Octahedral

96
Q

What does a colorimeter measure

A

Absorbance of light by a coloured sample

97
Q

Draw the colour wheel which we use to predict colour of of light absorbed

A

Starting at 12 o’clock going clockwise: Red, Yellow, Green, Pale blue, Dark blue, Magenta

98
Q

State the 5 steps in measuring the concentration of transition metal ions in solution using colorimetry

A

1 - Set colourimeter to zero
2 - White light is filtered into a narrow range of frequencies producing monochromatic light
3- Monochromatic light passes through a sample held in a cuvette (some light is absorbed)
4 - Light which isn’t absorbed travels to the detector
5 - Draw a calibration graph by making up known concentration of metal solution and plot measured absorbance ( Then draw line of best fit)

99
Q

How do we set a colorimeter to zero

A

Measure absorbance of a blank sample (H2O)

100
Q

What colour must the colour produced from the filter be the same as in using colourimetry to measure the concentration of transition metal ions in solution

A

The colour absorbed by the metal ion in solution

101
Q

What does a detector do in colourimetry

A

Measures the level of absorbance against the blank sample

102
Q

What are 3 advantages of using colourimetry to measure the concentration of transition metal ions in solution

A

Quick
Cheap
Non - destructive

103
Q

What are the 2 conditions required to use colourimetry to measure the concentration of transition metal ions in solution

A

Reactant for which the concentration is being measured must be coloured
All other reactants and products aren’t coloured

104
Q

What are 2 disadvantages of using colourimetry to measure the concentration of transition metal ions in solution

A

Can’t analyse colourless substances
Errors from similar colours

105
Q

When can a colour change of a transition metal ion complex occur

A

When there is an exchange/substitution of ligands

106
Q

Write the equation for the reaction of (Co(H2O)6)²⁺(aq) with excess NH3(aq). State the shape and colour of reactant and product complexes

A
107
Q

Write the equation for the reaction of (Cu(H2O)6)²⁺(aq) with excess NH3(aq). State: what type of substitution this is, and the shape and colour of reactant and product complexes

A

Partial substitution

108
Q

Give an example of 2 monodentate ligands of a similar size

A

H2O
NH3

109
Q

How many Cl- ligands can fit in a transition metal complex

A

4

110
Q

Write the equation for the reaction of (Co(H2O)6)²⁺(aq) with Cl-(aq). State the shape and colour of reactant and product complexes

A
111
Q

Write the equation for the reaction of (Cu(H2O)6)²⁺(aq) with Cl-(aq). State the shape and colour of reactant and product complexes

A
112
Q

Write the equation for the reaction of (Fe(H2O)6)³⁺(aq) with Cl-(aq). State the shape and colour of reactant and product complexes

A
113
Q

Which type of ligands form stronger bonds and therefore more stable complexes in a metal ion complex:
Monodentate
Bidentate
Multidentate

A

Multidentate ligands form stronger bonds and therefore complexes that are stronger

114
Q

What is the chelate effect

A

An increase in entropy and therefore stability of a complex

115
Q

Explain how ligand substitution from a monodentate ligand to a multidentate ligand displays the chelate effect

A

Creates a solution with more particles and therefore an increase in entropy and stability

116
Q

What does a reaction with increasing entropy mean about the ease of reversibility of the reaction

A

Difficult to reverse since the reverse reaction would have a decrease in entropy, and delta H is often small as energy breaking/making is similar, therefore reaction not feasible

117
Q

What 2 things are required to reduce VO₂⁺ to V²⁺

A

Zinc
Acidic solution

118
Q

Write the redox equation for the reduction of VO₂⁺ to VO²⁺

A
119
Q

Write the redox equation for the reduction of VO₂⁺ to V³⁺

A
120
Q

Write the redox equation for the reduction of V³⁺ to V²⁺

A
121
Q

How many steps does it take to reduce VO₂⁺ to V²⁺

A

3

122
Q

What do redox potentials tell us

A

How easily an ion is reduced

123
Q

Explain the relationship between the stability of an ion and its redox potential

A

The least stable ions have the largest redox potential and are more likely to be reduced

124
Q

Why might difference in redox potential values in the data book be different to the values obtained in an experiment

A

Alterations in standard conditions
Type of ligand bonded
pH

125
Q

Give 2 factors which affect redox potential values

A

Type of ligand bonded
pH

126
Q

Explain how the type of ligand bonded to a metal ion affects its E°

A

E° always measured in aqueous solution (metal ion surrounded by H2O ligands)
So E° can be higher or lower than standard value if other ligands are bonded which may form stronger or weaker bonds affecting E°

127
Q

Explain how pH affects E° of a transition metal ion

A

The more acidic (lower pH) the larger the E° and therefore the ion is more easily reduced

128
Q

What is tollens used for

A

To distinguish between aldehydes and ketones

129
Q

Ag+(aq) + e- ⇌ Ag(s) E°= +0.80V
What does this mean about how easily Ag+ is reduced

A

Ag+ is easily reduced to Ag

130
Q

How is tollens reagent made

A

By reacting enough NH3(aq) to aqueous silver nitrate

131
Q

What is the formula for tollens reagent

A

(Ag(NH3)2)+

132
Q

What colour is tollens reagent

A

Colourless

133
Q

What happens when we add tollens reagent to an aldehyde

A

Ag+ reduced to Ag(s) (silver mirror)
Aldehyde is oxidised to a carboxylic acid

134
Q

What is the general redox equation for when we add tollens reagent to an aldehyde

A

RCHO(aq) + 2(Ag(NH3)2)+(aq) + 3OH-(aq) –> RCOO-(aq) + 2Ag(s) + 4NH3(aq) + 2H2O(l)

135
Q

Can ketones be oxidised by tollens reagent

A

No

136
Q

What can we do to find the concentration of a reducing agent (Fe2+/C2O42-)

A

Titrate against an oxidising agent (MnO4-)

137
Q

What are the 5 steps in finding the concentration of (Fe2+/C2O42-) in a redox titration - state colour changes for each

A

1- Place reducing agent (Fe2+/C2O42-) in a conical flask (unknown conc & vol) and add excess H2SO4
2- Place oxidising agent MnO4- in burette (known conc)
3 - Add MnO4- to conical flask until faint colour of MnO4- disappears (drop by drop near end point) - Purple to colourless for Fe2+/Colourless to light pink for C2O4-)
4- Read from bottom of meniscus at eye level how much MnO4- is added
5 - Record results to 2 D.P & repeat until you get 2 concordant results

138
Q

Why do we add excess H2SO4 to the reducing agent in a redox titration

A

Ensures the presence of sufficient H+ ions to allow reduction of oxidising agent

139
Q

What ion does MnO4- form when it is reduced

A

Mn2+

140
Q

What ion does Cr2O72- form when it is reduced

A

Cr3+

141
Q

What does O2 form when it is reduced

A

H2O

142
Q

What does C2O4- form when it is oxidised

A

CO2

143
Q

What ion foes Fe2+ form when it is oxidised

A

Fe3+

144
Q

What is the half equation for when FeC2O4 is oxidised

A

FeC2O4 —> 2CO2 + Fe3+ + 3e-

145
Q

What is the half equation for the reduction of MnO4-

A

MnO4- + 8H+ + 5e- –> Mn2+ + 4H2O

146
Q

What is the half equation for the reduction of Cr2O72-

A

Cr2O72- + 14H+ + 6e- → 2Cr3+ + 7H2O

147
Q

What is the half equation for the reduction of O2 to form water

A

O2 + 4H+ + 4e- —> 2H2O

148
Q

What is the half equation for the oxidation of C2O42-

A

C2O42- → 2CO2 + 2e−

149
Q

What are the stages in balancing a half equation

A

1 - Balance elements through coefficients (non Hydrogens or oxygens)
2- Balance oxygens with H2O
3- Balance H’s with H+
4- Balance charge with e-

150
Q

What is an oxidising agent

A

A species which is reduced

151
Q

What is a reducing agent

A

A species which is oxidised

152
Q

What is the half equation for the oxidation of Fe2+

A

Fe2+ —> Fe3+ + e-

153
Q

What are the two types of catalyst

A

Homogeneous
Heterogeneous

154
Q

What is a heterogeneous catalyst

A

A species that increases the rate of a reaction by providing an alternative reaction pathway of a lower activation energy, which is in a different state to reactants

155
Q

Give an example of the use of a heterogeneous catalyst

A

Haber process
Solid iron catalyst is used
Reactants are all gasses and so Fe is a heterogeneous catalyst

156
Q

Explain how increasing the surface area of a heterogeneous catalyst can increase the rate of reaction

A

More particles available to react at any given time

157
Q

What is a homogeneous catalyst

A

A species that increases the rate of a reaction by providing an alternative reaction pathway of a lower activation energy, which is in the same state as reactants

158
Q

How do homogeneous catalysts form intermediates

A

By combining with reactants to form products (the catalyst is then always reformed)

159
Q

Why are transition metals good catalysts

A

They have variable oxidation states -they receive and loose some e- in d orbitals to speed up reactions

160
Q

What is the contact process

A

The use of vanadium to make H2SO4

161
Q

State the species and type of catalyst used in the contact process

A

V2O5
Homogeneous

162
Q

What reaction does V2O5 in the contact process

A

SO2 to SO3

163
Q

Write the 3 steps in the contact process with equations, and stating which species is oxidised/reduced in each step

A
164
Q

What is the purpose of using a catalyst

A

Faster & lower temperature required which saves money & energy and is also better for the environment

165
Q

How can impurities cause catalytic poisoning

A

Impurities bind to the surface of a catalyst which blocks the active sites for reactants to adsorb

166
Q

How does catalytic poisoning decrease the rate of reaction

A

Catalytic poisoning decreases the surface area of a catalyst

167
Q

Give an example of catalytic poisoning. State what the impurity is and what it forms when it adsorbs to the surface of the catalyst

A

Haber process
H2 is made from methane which contains sulphur impurities
Sulphur which isn’t remove will absorb to the surface forming iron sulphide which makes the iron catalyst less efficient

168
Q

What is the equation for the Haber process

A

N2(g) + 3H2(g) —> 2NH3(g)

169
Q

State 2 reasons why catalytic poisoning is bad

A

Lowers amount of product made
Catalyst needs to be cleaned or replaced more often
(These increase the cost of the whole process)

170
Q

Sketch the energy profile for a homogeneous catalyst

A
171
Q

What is the overall equation for the oxidation of iodide ions using S2O8-

A

S2O8-(aq) + 2I-(aq) —-> I2(aq) + 2SO42-(aq)

172
Q

Why is the uncatalysed reaction of the oxidation of iodide ions using S2O8- very slow

A

Reacting two negatively charged ions and so they repel, meaning a high activation energy

173
Q

What catalyst is used in the oxidation of iodide ions using S2O8-. State what type of catalyst this is

A

Fe2+(aq)
Homogeneous catalyst

174
Q

Write the two equations displaying the use of an Fe2+ catalyst in the oxidation of iodide ions using S2O8-. State the intermediate formed

A

(1) S2O8-(aq) + 2Fe2+(aq) —-> 2Fe3+(aq) + 2SO42-(aq)
Fe3+ is intermediate which reacts with I- to produce I2:
(2) 2I-(aq) + 2Fe3+(aq) —> 2Fe2+(aq) + I2(aq)
Catalyst reformed

(Combine both equations to get overall equation)

175
Q

What is the test for iodine

A

Starch solution
Blue/black = positive result

176
Q

What is an autocatalyst

A

A type of homogeneous catalyst where the product catalyses the reaction

177
Q

Give an example of autocatalysis

A

Mn2+ is a catalyst in the reaction between C2O42- and MnO4-
(Mn2+ is product & catalyst)

178
Q

State what the presence of an autocatalyst means about the rate of a reaction

A

As the reaction proceeds, amount of product increases and therefore the rate of reaction also increases due to more catalyst present

179
Q

What is the overall equation of the reaction between MnO4- and C2O42-

A
180
Q

Why is the initial reaction between MnO4- and C2O42- very slow

A

Reacting two negative ions together and so a high activation energy

181
Q

Write the two steps for the autocatalysis reaction between MnO4- and C2O42-

A
182
Q

Draw the routes for Fe

A
183
Q

Draw the routes for Cu

A

Chemistry (Inorganic) (6 decks)

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