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Inorganic Chemistry > Transition Metals > Flashcards

Transition Metals Flashcards

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1
Q

Define ‘transition metal’

A

Forms at least one stable ion with a partially filled d-sub level

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2
Q

Are Scandium and zinc transition metals?

A

NO

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3
Q

What is special about Cu and Cr?

A

Their 4s only goes 4s1

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4
Q

What do the transition metals’ characters stem from?

A

Their partially filled d-sub level

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5
Q

What are the characteristics of transition metals?

A

Complex formation

Form coloured ions

Variable oxidation states

Catalytic activity

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6
Q

What is a ligand?

A

An electron pair donor

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7
Q

What is a complex?

A

A central metal ion/atom surrounded by ligands joined by coordinate bonds

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8
Q

What is coordination number?

A

The number of coordinate bonds to the central metal atom/ion

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9
Q

What is a coordinate bond?

A

When a molecule/ ion donates both the electrons from a lone pair to the empty orbital of another species

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10
Q

Define monodentate ligands

A

Donates one e- pair or forms one coordinate bond

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11
Q

Give the

a) Shape name
b) Bond angle
c) Occurrence

Of complexes with a coordination number of 2

A

a) linear
b) 180
c) Ag+ complexes

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12
Q

Give the

a) Shape name
b) Bond angle
c) Occurrence

Of complexes with a coordination number of 4

A

a) Square planar
b) 90
c) Pt2+ and Ni2+

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13
Q

Give the

a) Shape name
b) Bond angle
c) Occurrence

Of complexes with a coordination number of 4 when the ligands are too big to fit 6

A

a) tetrahedral
b) 109.5
c) eg Cl-

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14
Q

Give the

a) Shape name
b) Bond angle
c) Occurrence

Of complexes with a coordination number of 6

A

a) octahedral
b) 90
c) most complexes with small ligands (eg H2O and NH3)

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15
Q

Give an example of a linear complex

A

[Ag(NH3)2]+

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16
Q

Give an example of a tetrahedral complex

A

[CuCl4]2-

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17
Q

Give an example of a square planar complex

A

[Pt(NH3)2(Cl)2]

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18
Q

Give 2 examples of an octahedral complex

A

[Fe(H2O)6]2+

[Cr(NH3)6]3+

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19
Q

Why does the complex ion of Chloride ligands have a different shape to those of water ligands?

A

Chloride ions are too big to fit more than four around one ion

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20
Q

How does Cis-trans isomerism occur?

A

The complexes are locked into their current form

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21
Q

What does cis imply?

Trans?

A

“On the same side” - the same ligands are next to each other

“Opposite”- the same ligands are opposite (180 degrees from) each other

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22
Q

What is cis-platin used for?

Would trans-platin work?

A

As an anti-cancer drug

No

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23
Q

What are the possible side effects of cis-platin?

A

Hair loss
Fertility problems
Nausea

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24
Q

How do you minimise the side effects of cis-platin?

A

Use lowest dose possible

Target specific areas of the body

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25
Q

What general formula do complexes need for cis/trans isomerism to occur?

What would the B bond angles be for

a) cis
b) trans?

A

[M(A)4(B)2]

a) 90 degrees
b) 180 degrees

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26
Q

Define bidentate ligand

A

Forms 2 coordinate bonds with a transition metal ion

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27
Q

What must a ligand have to be able to be bidentate?

A

2 available lone pairs to form coordinate bonds

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28
Q

3 Ethyl diamine ligands form coordinate bonds with a metal ion. The complex ion has a coordinate number of 6. What is its shape?

A

Octahedral

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29
Q

Give 3 features of optical isomers

A

They have no plane of symmetry

They are non-superimposable mirror images of each other

They differ in the direction with which they rotate plane-polarised light

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30
Q

Which complex ions show optical isomerism?

A

Octahedral complexes formed from bidentate ligands

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31
Q

Define multidentate ligand

A

Forms 2 or more coordinate bonds to a transition metal ion from different atoms on the same ligand

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32
Q

Give the number of ligands, coordinate number, and shape of [M(EDTA)]2-

A

1 ligand
Coordinate number: 6
Shape: octahedral

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33
Q

On EDTA4- where are the lone pairs that form coordinate bonds?

A

On the single bond negative oxygens and Nitrogen’s

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34
Q

Why is EDTA most effective in alkaline conditions?

A

OH- reacts with H+

Equilibrium shifts to the right, ensuring EDTA can form 6 coordinate bonds

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35
Q

Give the general formula for a complex ion containing ethanedioate ions (M=2+)

Give the number of ligands and coordinate number

A

[M(C2O4)3]4-

3 ligands

Coordinate number: 6

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36
Q

Where are the lone pairs on the C2O4 2- ion?

A

On the negative single bond oxygens

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37
Q

Where are the lone pairs on ethyl diamine?

A

On the nitrogens

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38
Q

How does EDTA soften water?

A

By reacting with and removing Mg2+ and Ca2+ ions

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39
Q

What is EDTA used for in medicine?

A

To treat people with lead poisoning in a treatment called chelation therapy

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40
Q

How does chelation therapy work?

A

EDTA makes the toxic ions present in the body harmless

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41
Q

What is the molar ratio of metal:EDTA complexes

A

1:1

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42
Q

What kind of titration is EDTA used in?

What is usually in the burette?

A

Complexometric titrations, to calculate the concentration of metal positive ions in aqueous Solutions

EDTA

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43
Q

What is the chelate effect?

A

A multi-dentate ligand will always displace a uni-dentate ligand due to the increase in entropy

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44
Q

What colour is seen at the end of complexometric titrations?

What indicators are usually used?

A

The colour of the “free indicator”

Organic dyes, which show one colour as a ligand in a complex with a metal ion and another when not part of a complex

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45
Q

Why is oxygen not a very good ligand with haemoglobin?

A

They are weakly bonded so the oxygen can be readily given up to cells

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46
Q

Why is CO poisonous?

A

It can also bind to haemoglobin, preventing the transport of oxygen

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47
Q

What does a haem unit consist of?

How is haemoglobin formed?

A

A porphyrin ring coordinately bonded to Iron

When a haem is bonded to a globular protein

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48
Q

What is the coordination number of a porphyrin ring?

What does it consist of?

A

4

Fe coordinately bonded to 4 Nitrogen

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49
Q

Why does the chelate effect occur?

A

Mono-dentate are substituted by multi-dentate ligands to create a more stable complex

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50
Q

How can a more stable complex be formed?

A

A ligand substitution reaction

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51
Q

Explain why the entropy increases for the chelate effect

A

The number of moles increases

Disorder increases

Entropy change in positive

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52
Q

In a ligand substitution reaction why is 🔺H = 0?

Why is it feasible?

A

bonds broken and formed are equal

Mole number increases, so disorder increases, so enthalpy change is positive
Therefore T🔺S > 🔺H so 🔺G<0

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53
Q

Describe the practical method to fund the mass of a complex ion using titration

A

Filter solution
Wash solid with solvent/water to remove soluble impurities
Allow to dry in oven
Heat product to constant mass

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54
Q 
In recrystallisation, why is 
a) a minimum volume of hot ethanol
b) the solution is filtered hot
c) cool the filtrate in ice to form crystals
Important?
A

a) to form a saturated solution, which maximises yield
b) to remove INSOLUBLE impurities
c) remove soluble impurities

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55
Q

Why do transition metal ions give such different colours?

A

Partially filled d-sub levels
Electrons can shift up and down between unoccupied orbitals
This is called electron promotion

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56
Q

What is 🔺E?

A

Energy gap between orbitals

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57
Q

Explain why metal ions are coloured

A

d-orbitals split in energy levels
e- are promoted to higher energy d-orbitals by absorbing energy in the form of light
The colour transmitted and observed is the light not observed

58
Q

What are the equations for 🔺E?

A

🔺E= hv

🔺E= hc/(wavelength)

59
Q

What is h?

A

Planck’s constant

60
Q

What is v?

A

Frequency of light absorbed

61
Q

What is c?

A

Speed of light

62
Q

How do you convert nanometers to metres?

What is the symbol for nanometers?

A

x10-9

nm

63
Q

Units for frequency of light

A

s-1

64
Q

Units for wavelength

A

m

65
Q

Units for 🔺E

A

J

66
Q

What 3 things can be done to change the 🔺E?

What do these changes result in?

A

Change the ligands bonded to the metal ion
Change the coordination number
Change the oxidation state of the metal ion

The complex to change colour

67
Q

What should an absorbable vs concentration graph look like?

A

A straight line through the origin

68
Q

A solution of KMnO4 has an unknown concentration

Describe briefly how colourimetry can be used to determine the concentration of this solution

A

Make samples of KMnO4 with known concentrations
Add ligand to make colour more intense
Find lambda max and set colourimeter to this wavelength
Plot a graph of conc./ moldm -3 (x-axis) vs absorbance (y)
Find absorbance of unknown on y, go across to line and find corresponding x coordinate

69
Q

If you’re unsure how to do a calculation, what can you try to use?

A

The units

70
Q

When testing for aldehydes, what uses transition metals’ variable oxidation states?

A

Fehling’s Solution

Cu2+ reduced to Cu+1(brick red colour) by an aldehyde

71
Q

When testing for alcohols, what uses transition metals’ variable oxidation states?

A

Cr(+6) in acidified potassium dichromate is reduced to Cr(+3) by alcohols

72
Q

What is a suitable reducing agent for vanadium (V)

A

Zinc and an acid (generally HCl)

73
Q

How is the flask stoppered in the reduction of Vanadium (V)?

Why?

Why is bung not used?

A

With cotton wool

Allows Hydrogen to escape while preventing too much air from entering which would re-oxidise lower oxidation states of Vanadium

Would cause a build up of pressure

74
Q

What colour is vanadium (+5)?

A

Yellow

75
Q

What colour is vanadium (+4)?

A

Blue

76
Q

What colour is vanadium (+3)?

A

Green

77
Q

What colour is vanadium (+2)?

A

Purple

78
Q

How do you re-oxidise vanadium’s Lower oxidation states?

A

With oxygen in air

OR

nitric acid

79
Q

Why is nitric acid used to re-oxidise vanadium?

A

O2 takes too long

80
Q

Why is the reduction of vanadium done in acidic conditions?

Why is there fixing during this experiment?

A

To provide H+ ions

Hydrogen is produced. Zinc reacts with an acid - metal+acid—-> salt + H2

81
Q

What is the colour change is a redox reaction with MnO4- ?

What makes pink?

Why is an indicator not needed?

A

Colourless to pink

One extra drop of MnO4-

MnO4-‘s colour changes distinctly as it changes oxidation state

82
Q

What is often used as an oxidising agent to analyse Fe2+ and C2O4 2-?

What is Fe2+ oxidised to?

What is C2O4 2- oxidised to?

A

Acidified MnO4-

Fe3+

CO2

83
Q

What is the oxidation half equation for C2O4 2-?

A

C2O4 2- —-> CO2

84
Q

What is the oxidation half equation for Fe2+?

A

Fe2+ ——> Fe3+

85
Q

What is the reduction half equation for MnO4-?

What can you use this to form?

A

MnO4- —-> Mn2+

The full equation for the oxidation of C2O4 2- and the equation for the oxidation of Fe3+

86
Q

What conditions does the MnO4- Solution need for a redox titration?

What do we use for this?

A

Acidified

Sulphuric acid

87
Q

Why do we not use HCl to acidify a Solution of MnO4- ions?

A

emf MnO4-/Mn2+ > emf Cl2/Cl-
HCl contains Cl-
Therefore MnO4- reduced to Mn2+ and Cl- is oxidised to Cl2
This would give a larger titre value

88
Q

What is the molar ratio of Fe2+:MnO4-?

A

5:1

89
Q

What is the molar ratio of

C2O4 2-:MnO4-?

A

5:2

90
Q

Why can transition metals be used as catalysts?

A

Their partially filled d-block orbitals mean they have variable oxidation states

91
Q

What is a catalyst?

A

A substance that increases the rate of reaction but isn’t used up in the reaction

92
Q

How does a catalyst work?

A

Provides an alternative reaction route with a lower Ea

93
Q

How does a catalyst affect equilibrium?

A

No effect on position of equilibrium as it increases forwards and backward reactions equally
Only decreases time taken to reach equilibrium

94
Q

What catalysts can be used in a catalytic converter?

What are they sprayed on and why?

A

Platinum, palladium, rhodium

A ceramic honeycomb structure to limit costs and maximise surface area

95
Q

Define heterogeneous catalyst

A

Catalyst in a different state to the reactants (usually a solid) in

96
Q

What are important examples of heterogeneous catalytic processes?

A

Haber

Contact process

97
Q

How does a solid catalyst work?

3 marks

A

Reactants adsorbed onto active sites on catalyst surface

Reaction occurs with a lower Ea as bonds are weakened or new bonds are made on the surface

The products are desorbed

98
Q

How do you maximise the efficiency of a solid catalyst?

A

Use a thin coating of it on a honeycomb structure to increase surface area

99
Q

What catalyst is used in the Haber Process?

What is the reaction?

A

Fe(s)

N2(g) + H2(g) [equilibrium] 2NH3(g)

100
Q

What does the contact process make?

A

SO3 which can be added to water to make Sulphuric acid

101
Q

What is the catalyst in the Contact Process?

A

Vanadium (V) Oxide

V2O5(s)

102
Q

What are the 2 steps for the contact process?

A

SO2(g) + V2O5(s) —> SO3(g) +V2O4(s)

V2O4(s) + 0.5O2(g) —> V2O5(s)

103
Q

What is the overall equation for he Contact Process?

A

SO2(g)+0.5O2(g)—> SO3(g)

104
Q

How is a catalyst poisoned?

A

Impurities adsorb strongly to the surface, blocking active sites.
This lowers the efficiency and can be extremely difficult to remove, ruining the catalyst which is v costly

105
Q

How do you avoid catalyst poisoning

A

Purify reactants

106
Q

Define homogenous catalyst

What does the reaction pathway often involve?

A

A catalyst that is the same phase as the reactants (usually taking place in a solution)

An intermediary

107
Q

Give overall equation for I- and Peroxodisulfate

Don’t balance now, balance in exam

A

S2O8 2- + I- —> SO4 2- + I2

108
Q

Give 2 steps for the catalysed reaction of I- and S2O8 2-

Don’t balance now, balance in exam

A

One: S2O8 2- + Fe2+ —-> SO4 2- + Fe3+

Two: Fe3+ + I- —-> Fe2+ + I2

109
Q

What is autocatalysis?

A

When one product from a reaction is a catalyst for the reaction

110
Q

How does the speed of reaction go for autocatalysis?

A

Starts slowly
Rate increases when catalyst is produced
Slows again when reactants run out

111
Q

What is the equation for the oxidation of ethanedioate ions to CO2?

(Don’t balance now, balance in exam)

A

C2O4 2- —> CO2

112
Q

What is the half equation for the reduction of MnO4-?

Don’t balance now, balance in exam

A

MnO4- —-> Mn2+

113
Q

Why is the reaction of ethanedioic acid and MnO4- originally very slow?

This is an autocatalysis reaction. What is the catalyst?

A

It involves the reaction of 2 negative ions which repel is collision is difficult

Mn2+

114
Q

What are the catalysed steps for C2O4 2- + MnO4-?

Don’t balance now, balance in exam

A

One: MnO4- + Mn2+ —-> Mn3+

Two: Mn3+ + C2O4 2- —-> Mn2+ +CO2

115
Q

Why can Mn2+ act as a catalyst?

A

It has variable oxidation states of +2 and +3

116
Q

Describe the autocatalysis concentration vs time graph

A

Slow rate in beginning as no catalyst is present
Then becomes steeper because it speeds up when catalyst is produced
Slows and eventually stops when reactants are used up

117
Q

Why is the overall reaction for I- + S2O8 2- very slow?

How does a catalyst help?

Can both Fe2+ and Fe3+ be used as a catalyst? What does this mean?

A

Two negatively charged species are reacting together
This results in a high Ea as ions repel each other

Introduces a positive species

Yes: catalytic steps can happen in either order

118
Q

Give examples of catalytic poisoning

A

Lead poisoning in catalytic converters in cars from leaded petrol, which can poison both Pt and Rh

Sulphur poisoning in Haber Process. H2 is obtained from natural gas and can be contaminated by sulphur which can poison the Fe (sulphur is added to natural gas to give it an odour to detect leaks)

119
Q

Why do different complexes have different colours?

A

d orbital splitting is different
Light is absorbed for e- promotion
Different frequency of light absorbed for different complexes due to different 🔺E

120
Q

Ratio of Fe2+: chromate ions

A

6:1

121
Q

What is the shape of cisplatin

A

Square Planar

122
Q

Name elements which are likely to form square planar complexes

A

Pt

Pd

123
Q

Why can a Lewis acid also be a Bronsted Lowry acid

A

All donate H+ and H+ readily accept e-

124
Q

Why are Fe3+ complexes more acidic than Fe2+

A

Fe3+ is a smaller ion with a higher charge
Therefore attracted to O in H2O more strongly, polarising H-O bond
This makes O-H bond weaker and more likely to break, releasing protons

125
Q

Exam answer for “why are all aqueous solutions of Fe3+ more acidic than Fe2+”

A

Fe3+ is smaller with a higher charge

Fe3+ polarises O-H bond MORE THAN Fe2+, releasing more H+ ions

126
Q

Is Al a transition metal

A

No

127
Q

Metal 3+ with carbonate general equation

A

Salt + CO2 + H2O

128
Q

Colour of copper aqua ion with carbonate

A

Blue green PPT

129
Q

Which reacts with excess NaOH

A

Al

130
Q

Which reacts with excess NH3

A

Cu

131
Q

Give colours of V oxides from 5 to 2

A

5- yellow
4 - blue
3 - green
2 - purple

132
Q

Colour of 5+ of V

A

Yellow

133
Q

4+ V

A

Blue

134
Q

+3 V

A

Green

135
Q

2+ V

A

Purple

136
Q

Which V oxide is purple

A

+2

137
Q

What colour is a mixture of V +5 and +4

A

Green

Because blue and yellow are green

138
Q

What is a suitable reducing agent for Vanadium

A

Zinc and an acid

Usually Zn and HCl

139
Q

Method for colorimetry

A

Make solutions of know conc of same metal (some more some less conc)
Add ligand to intensify colour
Set spectrophotometer to lambda max
Measure absorbance
Plot graph of absorbance vs concentration (calibration curve)
Measure absorbance of unknown and determine its conc from curve

140
Q

What is used in colorimetry?

A

Visible spectrophotometer or colorimeter

141
Q

What is lambda max

A

The wavelength at which absorbance is at a maximum

Inorganic Chemistry (6 decks)

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