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Chemistry (A2) > Transition Metals > Flashcards

Transition Metals Flashcards

1
Q

Define a Transition Metal

A

An Element which forms at least one stable ion with partially filled D-Sub Shell of electrons

Found within the d block

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2
Q

Where are Transition Metals located in the periodic table

A

part of the D-Block

In the middle (Ti- Cu)

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3
Q

What are some physical properties of transition metal (4)

A

Metallic

Good Conductor son heat and electricity

High Melting and boiling points

Strong,Shiny and Hard

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4
Q

What are some Uses of:
1) Iron
2) Titanium
3) Copper

A

1) Vehicle Bodies, To reinforce concrete

2) Aeronautical Parts Very strong and light

3) Cheap Wiring and plumbing

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5
Q

What’s are the chemical properties of transition Metals (4)

A

Variable Oxidisation States

Coloured Compounds/ Ions in solution

Good Catalysts

Forms Complex ions

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6
Q

Define the Term Complex Ion (2)

A

Central transition metal ion

Surrounded by ligands that are coordinately bonded (covalently) to it

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7
Q

Give examples of transition metal catalysts and the processes they Catalyse (3)

A

Iron - Haber Process

Vanadium (V) Oxide - Contact Process

Manganese (IV) Oxide - Decomposition of hydrogen peroxide

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8
Q

Which sub shell is emptied first when transition metals form ions

A

4s orbital

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9
Q

Define the Term Ligand (4)

A

An ion or molecule

with at least 1 lone pair of electrons

that donates the electrons to a transition metal ion

to form a coordinate bond & create a transition metal complex

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10
Q

Define the Term Unidentate ligand

A

A Ligand that donates 1 electron pair to form 1 coordinate bond to the central metal ion (only 1 lone pair to donate)

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11
Q

Define the Term bidentate ligand

A

A Ligand that donates 2 pairs of electrons to form two coordinate bonds to the central metal ion ( 2 lone pars to donate)

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12
Q

Define the Term Multidentate ligands

A

A Ligand that donates 3 or more electron pairs to form 3 or more coordinate bond to the central metal ion

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13
Q

Give some examples of monodentate ligands (4)

A

Cl-
H2O
NH3
CN-

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14
Q

Draw Ethanedioate ligand

A

Bidentate Ligand

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15
Q

Draw Benzene-1,2-diol Ligand

A

Bidentate Ligand

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16
Q

Draw an ethane-1,2-diamine ligand

A

Bidentate ligand

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17
Q

Define the term coordination Number

A

The number of coordinate bonds the metal ion has formed to surrounding ligands

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18
Q

What is the Chelate Effect (3)

A

Chelate Complexes with mulidentate ligands are favoured over ligands that are monodentate or bidentate ligands

more lone pairs per molecule

as it is a entropically favourable reaction

more moles of molecules on products then reactants

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19
Q

Explain the Chelate effect on ions in terms of entropy and the reaction that is occurring

A

Number of molecules increases when multidentate ligands displaces other ligands

that form fewer coordinate bonds with the central metal ion per molecule

so the products has more moles of molecules then products

entropically favorable

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20
Q

What ion is usually formed when a transition metal compound is dissolved in water

Draw an example

What is its Shape

A
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21
Q

If a transition metal ion has 2 ligands, which shape is it usually

A

Linear

180 Degrees

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22
Q

If a transition metal ion has 4 ligands

What shapes can it be

A

Tetrahedral

Square Planar

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23
Q

What shape is a complex ion if it has 6 ligands

A

Octahedral

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24
Q

How can Complex ions display E-Z isomerism (geometric)

What shapes does it apply to

A

Square Planar or Octahedral shapes

Where the metal complex has 2 or more ligand types

If the two high priority ligands are on the same side of the molecule this forms an E or cis- isomer (Reflection on x=O)

If the two high priority ligands are on opposite sides of the molecule this forms an z or trans- isomer

(Reflection on y=O)

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25
Q

What happens to Co2+ ,Cu2+ and Fe3+ ‘s coordination numbers when Cl- Ligands replace NH3 or H2O ligands

A

Coordination numbers decrease from 6 to 4

Cl- is a much larger ligand then H2O or NH3

Therefore the shape changes to tetrahedral or square planar

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26
Q

What is haem- (6)

A

A molecule which makes up protein chains

with an Fe2+ central metal ion

Complex has a coordination number of 6

4 of the coordinate bonds are to a ring system called porphyrin

1 is to the nitrogen of a globin (protein)

1 is to an oxygen in an O2 molecule

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27
Q

How does haemoglobin transport oxygen

A

O2 forms weak coordinate bond to the metal ion, then is transported around the body. The bond breaks when haemoglobin reaches cells and oxygen is released.

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28
Q

Why is Carbon monoxide toxic (3)

A

CO coordinator bonds to the Fe2+ within haem- that is very strong

It’s coordinately bonded more strongly then O2 or H2O to the central metal ion

Stops O2 from bonding to haemoglobin so O2 cannot be transported around the body.

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29
Q

Why are transition metal compounds coloured (6)

A

TM Ions have Partially filled D orbitals

When ligands are coordinately bonded to form complexes the d orbitals are split into different energy levels

For electrons to excite to a higher energy level energy in the form of photons is absorbed

Within TM the photons absorbed have a frequency within the visible light spectrum, as the photons energy must have the same energy as the energy gap between the split d subshells

The frequency of visible light absorbed is not visible to receptors

meaning a complimentary colour is visible made up of all colours not absorbed

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30
Q

What affects the colour of a transition metal compounds (3+1)

A

Type of Ligand

Shape of complex

Oxidisation state of the metal ion

All change the Energy gap between the split d orbitals

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31
Q
A
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32
Q

What can you use to reduce vanadium

A

Zinc

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33
Q

What colour is Fe2+

A

Pale Green

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34
Q

What colour is Fe3+

A

Pale Brown

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35
Q

What colour is Ni2+

A

Green

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36
Q

What Colour is Cr3+

A

green/Violet

more violet when its its aqua ion

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37
Q

What colour is Co2+

A

pink

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38
Q

What colour is Cu2+

A

Blue

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39
Q

What does a colorimeter do

A

Measures absorbance of a particular wavelength of light by a solution

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40
Q

What information does a colourimeter give you

A

The concentration of a certain ion in the solution

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41
Q

Why can transition metal form variable oxidisation states

A

Ions formed have partially filled d-orbitals
so loose electrons in the 4s and then 3d electrons

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42
Q

Which oxidation states do all transition metals have (except scandium)

A

+2
Due to loss of 2 electrons from 4s orbital

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43
Q
A

Tollens Reagent
Gentle oxidising agent
Used as a test for aldehydes ( Silver mirror formed with aldehyde)

silver 2 complex ions are reduced to form solid silver Precipitate

when in the presence of a molecule that can be oxifdised

44
Q

What colour is MnO4- ions?

A

Deep Purple

45
Q

What colour is a Mn2+ ion

A

Pale Pink

(Too faint to usually detect on a colorimeter)

46
Q

Write the half equation for the reduction of MnO4- to Mn2+

A

MnO4- + 8H+ +5e- ———>. Mn2+ + 4H2O

47
Q

Why are redox titrations with transition metals said to be self indicating

A

They often involve a colour change as the metal is changing oxidisation stage

48
Q

What colour Cr2O7 2- ion

A

Orange

49
Q

What Cr3+

A

Green

50
Q

Write a half equation for the reduction of Cr2O7 2- to Cr3+

A

Cr2O7 2- + 14H+ +6e- ————> 2Cr3+ +7H2O

51
Q

What happens to aqua metal ions in acidic conditions

A

They get reduced to a lower oxidation state

52
Q

what happens to aqua metal ions in alkaline conditions

A

they get oxidised

53
Q

What value signifies how readily will a metal ion reduce/ oxidise

A

E Cell values

More positive —> higher tendency to reduce

More negative —-> higher tendency to oxidise

54
Q

What changes the E Cell value of a TM metal ion complex

A

Ph, Ligands involved

55
Q

Define a Catalyst

A

A Substance that increases the rate of reaction via an alternate reaction pathway at lower activation energy without itself or any substance changing chemically

56
Q

Why are Transition Metals Good Catalysts

A

They Exist in variable Oxidation states

to provide more alternate reaction pathways for the reaction to potentially follow

57
Q

Why are Group 1,2,3 metals not as good catalysts as TM

A

They only exist in 1 oxidation state

58
Q

What are the advantages to using a catalyst in a reaction

A

Increases rate of reaction —-> lower activation energy —-> more particles above activation energy

Allows reaction at lower temperatures —> saves energy and resources

59
Q

What metals are used in a catalytic converter

What are the reactions they catalyse

A

Platinum, Palladium, Rubidium

60
Q

Define heterogeneous Catalyst (2)

A

A Catalyst that is in a different phase to the reactants

Catalyst activity occurs on the catalysts surface as the reactants pass over it

61
Q

What is an advantage of using a heterogenous catalyst over homogeneous

A

Catalyst is easily separated from products

62
Q

How do heterogenous catalysts work

A

Reactants adsorb to the catalysts surface at active sites

This weakens the bonds within the reactants

the reactants are then held close together in the correct orientation to react

After reaction has occurred the products desorb from the active sites

63
Q

For a heterogeneous catalyst to be considered good, what properties must it have (3)

A

reactants cant adsorb too strongly to the active sites - otherwise products wont desorb

reactants cant adsorb too weakly to the active sites - otherwise products wont be held for long enough for a reaction - bonds wont be sufficiently weakened

Need a good balance between desorption and adsorption

64
Q

How do you increase the efficiency of heterogeneous catalyst (2)

A

Increase surface area — Increases number of active sites present

Spread catalyst onto an inert surface —- increase the surface/mass ratio eg. ceramic honeycomb

65
Q

What is Catalyst poisoning

A

Unwanted impurities adsorb to the catalyst active sites too strongly

cannot desorb

This Block the active sites on the catalysts surface for the reactants to bind to

66
Q

What effect does catalyst poisoning have on catalytic activity

A

Decreases the effectiveness of the catalyst over time, as more active sites are blocked by impurities

67
Q

How can the effectiveness of a heterogeneous catalyst reduce other then catalyst poisoning

A

Finely divided catalyst can be gradually lost from their support surface

68
Q

Write the equation for the haber process, what is its conditions and catalyst

A

N2(g) + 3H2 (g) ——> 2NH3 (g)

Iron catalyst

400-450 degrees c

200atm

69
Q

How does the catalyst in the haber process get poisoned

A

The iron catalyst gets poisoned by sulphur impurities in the gas streams

as methane is used for the production of hydrogen gas, which contains sulphur impurities

70
Q

Write the overall equation for the contact process, what is its catalyst and conditions

A

1-2 atm

450 degrees c

71
Q

What are the 4 reactions that are involved in the contact process

A

3) SO3 + H2SO4 –> H2S2O7
4) H2S2O7 + H2O —> 2 H2SO4

72
Q

Why is vanadium (v) oxide good catalyst in the contact process

A

Can change oxidation state between 5+ and 4+

so can be reused

73
Q

Define homogeneous catalyst (4)

A

A catalyst that is in the same phase as the reactants

by forming an intermediate

creating a different reaction pathway with a lower activation energy

after intermediate is formed the original catalyst is reformed

74
Q

How do homogeneous catalysts work

A

Form Intermediates that give a different reaction pathway with lower activation energy

75
Q

What is the overall reaction between S2O8 2- and I- ions

(no catalyst)

A
76
Q

Why does the reaction between S2O8 2- ions and I- ios have a high activation energy in normal conditions

A

Two negative ions are reacting
they repel each other
so Ea is high

77
Q

What is the overall reaction between S2O8 2- and I- ions

(both reactions + fe2+ catalyst)

A
78
Q

Define the term autocatalysis

A

When a product of a reaction is also catalyses the original recation

Homogeneous Catalyst

79
Q

Draw and explain a concentration of reactant against time graph for an auto catalysed reaction

A
80
Q

Write the half equations for the conversion of C2O4 2- ions to CO2

A
81
Q

Write the combined half equation for the reaction between C2O4 2- and MnO4- ions

A
82
Q

In this reaction how does Mn2+ autocatalyse the original reaction

A

Mn2+ is oxidised then reduced

83
Q

total oxidation state of the metal complex (overall charge)

A

oxidation state of metal + total oxidation state of ligands

84
Q

What is a lewis base?

A

Lone pair donors

85
Q

What is a lewis acid?

A

Lone pair acceptor

86
Q

How to you create a colourimeter calibration graph

A

Absorption (y axis) varying known concentrations of transition metal solutions (x axis) is tested and plotted on a graph.

87
Q

What is a complimentary colour

A

Colour formed through the mixture of all visible light wavelengths that are not absorbed.

88
Q

Draw and explain the complimentary colour wheel

A

Find what colour the TM absorbs

Opposite to it is the complimentary colour

89
Q

Draw a cis- isomer for [Co (H2O)4 Cl2]

A
90
Q

Draw a trans- isomer for [Co (H2O)4 Cl2]

A
91
Q

Why is scandium and zinc not considered transition metals?

A

Sc3+ has an empty d subshell not partially filled so not a TM

Zn2+ has a full d subshell not partially filled so not a TM

92
Q

Explain why different TM complex ions have different colours (3)

A

In different complexes the energy gap between the split d orbital differs

When an electron is excited by absorbing energy

Different wavelengths in the visible light spectrum are absorbed, producing a different complimentary colour to a light receptor

93
Q

Why would a positive intermediate increase the rate of the overall reaction between 2 negative ions

A

The positive intermediate formed attracts the negative ions, decreasing the activation energy.

94
Q

Write an Equation for the reaction between 1,2- Diaminoethane and a Cu(NH3)4.(H2O)2 complex

Why is the enthalpy change approximately zero

A

4 Cu-N coordinate bonds are broken

4 Cu-N coordinate bonds are made after the ligand substitution

Both have very similar enthalpy resulting in an approximate zero enthalpy change

95
Q

What is the structural formula for 1,2- diaminoethane

A

H2N H2C CH2 NH2

Symmetrical molecule

96
Q

For a reaction between 1,2- Diaminoethane and a Cu(NH3)4.(H2O)2 complex

It has an approximately zero enthalpy change

Explain why the reaction occurs anyway

A

Chelate Effect

3 Particles react to form 5 particles

Disorder has increased so entropy change is positive

As free gibbs = Enthalpy change - T(Entropy Change)

It gives a negative free gibbs so the reaction is feasible

97
Q

What is the written complex for Silver (ii) Nitrate

A

[Ag(NH3)2]+

98
Q

1) See below
2) What property must an impurity within sample x have for the calculate mass to be larger then expected

A

1) Find out charge of TM ion

SO4 = 2-
H2O = 0
So Fe = 2+

Construct two half equations and combine them to form a redox equation (Equation for reaction)

2) Impurity must be a reducing agent that reacts with the dichromate

99
Q
A

Manganate would oxidise the Cl- ions

Because the E Cell for Manganate (VII) is more positive then the Ecell for Cl2

1.51 - 1.36 = 0.15 (Cl2 equation flipped but ECell is the same)

Meaning its a feasible reaction

100
Q

Write an equation between manganate (VII) ions and ethandioate ions in acidic conditions

Why can you use a colorimeter to measure the concentration of Manganate (VII) ions

A

Ethandioate is oxidised to 2CO2

Acidic conditions means lots H+’s to react

2) Consider the properties of products and reactions

Only Manganate(VII) ions are distinctly coloured
Mn2+ ions are plane pink and are too faint to detect.

101
Q

On a Concentration against time curve

What part of it shows an auto catalysed reaction

A

Reaction starts of slow shown by a shallow gradient

Then the rate gets faster shown by a Gradient increasing

102
Q

For a Reaction between manganate (VII) ions and ethandioate ions in acidic conditions

Identify the AutoCatalyst

Write Two Equations to show how the autocatalyst is involved

A

1) Mn2+ ions

2) Write equation between original reactant and autocatalyst forming the intermediate

Next equation show how the intermediate is reduced and the ethanedioate is simultaneously oxidised in a redox reaction

103
Q
A

A & C appear to have a reduction in oxidation state

however Both molecules of CrO4 2- have an os state of 6

6x2 = 12
12=12

so A is the only one reduced

104
Q

Explain what colour and why do Aqueous Solutions containing [CuCl4]2-appear coloured (1+2)

A

Yellow/PaleBrown

Only Particular light wavelengths absorbed, this excites electrons

Only Yellow light is transmitted which is a complimentary colour consisting of all non absorbed wavelengths

105
Q

What oxidation state is EDTA ligand?

A

4-

106
Q

Explain why colourimetery cannot be used to identify the concentration of solutions containing [CuCl2]-

A

For this to occur Cu metal ion has to have an oxidisation state of 1

a Cu+ ion has a full 3d sub shell of electrons, as the 1 electron in the 4s orbital is emptied first.

This means that there is no split d orbital

So The metal ion appears colourless as it cannot absorb frequencies of visible light

Chemistry (A2) (15 decks)

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