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Chemistry > Transition Metals > Flashcards

Transition Metals Flashcards

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1
Q

What is a ligand

A

An atom, ion or molecule which can donate a lone pair of electron.

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2
Q

Define coordinate bonding

A

It is when the shared pair of electrons in the covalent bond come from only one of the bonding atoms

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3
Q

What is coordination number

A

The number of coordinate bonds formed to a central metal ion

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4
Q

Give examples of monodentate, bidentate and multidentate ligand

A

Monodentate : Cl-, H2O, NH3
Bidentate : NH2CH2CH2NH2 and C2O4^2- (ethanedioate ion)
Multidentate : EDTA^4- can form 6bonds

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5
Q

Give equation of incomplete substitution reaction between copper and ammonia, then state the colour change

A

[Cu(h2o)6]^2+ + 4NH3 -> [Cu(Nh3)4(h2o)2]^2+ + 4H2o

From pale blue to deep blue solution

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6
Q

Why would there be a change in coordination number when Cl ligand is involved

A

Cl- is a larger ligand than the uncharged h2o and nh3

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7
Q

When [Cu(h2o)6]^2+ is reacted with Cl ligand, what forms and state the colour change

A

[CuCl4]^2-

Yellow/green solution

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8
Q

If solid copper chloride (or any other metal) is dissolved in water, what does it form?

A

Aqueous [Cu(h2o)6]^2+ complex forms

NOT the CuCl4 complex!!!

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9
Q

Colour of [CoCl4]^2-

A

Blue solution

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10
Q

When would partial substitution of ethanedioate ions occur

A

When dilute aq solution containing c2o4^2- ions are added to a solution containing aq Cu2+
4 h2o will be replaced

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11
Q

Give an example of an iron(ii) complex with a multidentate ligand

A

Ahem

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12
Q

How does Fe(ii) in haemoglobin work in the body

A

In the body both H2O and O2 bind to Fe2+ ions as ligands, so the complex can transport O2 two where it’s needed then swap to h2o molecule.
In lungs where O2 concentration is high, water ligands are substituted for O2 molecules to form oxyhaemoglobin which is carried around body in blood

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13
Q

How can CO harm human in terms of haemo

What are the impacts on the human

A

CO is toxic to humans as it can form a strong coordinate bond with haemoglobin.
This is a stronger bond than that made with oxygen and so it replaces the oxygen attaching to the haemoglobin

impact - cause dizziness, headaches, even death

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14
Q

Chemical properties of transition metals, name 4 and what is it caused by

A

Form complex ions
Various oxidation states
Form coloured compounds
Good catalysts

These are caused by presence of an incomplete d sub shell

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15
Q

Physical properties of transition metals and question why

A

High density
Good electricity conductor
High melting and boiling point
- due to metallic bonds formed, electrostatic force of attraction between positive ions and sea of delocalised electrons

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16
Q

In period 4, which 2 are not transition metals, and why

A

Sc and Zn
Sc is 3d1 4s2, it must form Sc3+ ions so there would be no electrons in the d she’ll.
Zn is 3d10 4s2, when it forms Zn2+, there would be a full d she’ll

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17
Q

Why is electronic configuration of
Cr: [Ar] 3d54s1 and
Cu: [Ar] 3d10 4s1

A

For Cr, it prefers one electron in all 3d sub shell, making it more stable
For Cu, it prefers a full 3d sub shell, making it more stable as well

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18
Q

What is the chelate effect

A

The substitution of monodentate ligand with a bidentate or multidentate ligand leads to a more stable complex

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19
Q

Redox potentials tell you how easily it is reduced to a lower oxidation state. The more positive it is the more/less stable is it and the more or less likely will it be reduced

A

The more positive, the less stable, and the more likely it will be reduced

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20
Q

What 2 factors affect redox potentials in transition metal chemistry

A

Ph

Ligands (depends on how well they bind to the metal ion)

21
Q

Formation of coloured ions is associated with incomplete d orbital, what are the 3 things that cause colour changes to arise from?

A

Changes in
Oxidation state
Ligand
Coordination number

22
Q

Colour of [Co(NH3)6]2+

A

Yellow

23
Q

Colour of [Co(NH3)6]3+

A

Brown

24
Q

Colour of change of Co(H2o)6^2+ + 4Cl- -> [CoCl4]2-

A

Pink to blue

25
Q

How colour arises

A

Colour arises from electronic transitions from the ground state to excited states : between d orbitals

A portion of visible light is absorbed to promote d electors to higher energy levels. The light that is not absorbed is transmitted to give the colour we see.

26
Q

Give the equation that links the frequency of light absorbed with energy difference between the split d orbitals.

A

Difference in Energy =hv
Energy (J)
H=plancks constant (J)
V=frequency of light absorbed (Hz/s^-1)

27
Q

The colour absorbed and the colour we see is demonstrated by the relationship of complementary colours what method could you use to find out

A

Draw a circle with 6 fractions - write red orange yellow green blue green

28
Q

What would alter the energy split between d orbitals and thus changing frequency of light absorbed

A

Changing a ligand or coordination number

29
Q

Why does scandium not have a colour

A

It’s ion is Sc3+, it hasn’t got any d electrons to move around, so there’s no energy transfer

30
Q

Why’s ther no colour in Zn2+ and Cu+

A

They have full d shells, no space for electrons to transfer

31
Q

What’s a spectrometer and what does it do?

A

It is used to determine the concentration of solution by measuring how much light it absorbed.

It contains a coloured filter. The colour of filter is chosen to allow wavelengths of light through that to be most strongly absorbed by the coloured solution. ( more concentrated solutions absorb more light )

32
Q

If complexes have pale Colour and we’re unable to investigate through spectrometer, what can we do?

A

Add a suitable ligand to intensify the colour

33
Q

Vanadium has 4 main oxidation states, what are they and what are their colours.

Adding what would reduce vanadium down through each states?

A

V 5+ Yellow
V 4+ Blue
V 3+ Green
V 2+ Violet

Adding zinc

34
Q

Colour of MnO4- and Mn2+

A

MnO4- purple

Mn2+ colourless

35
Q

Which acid must be used for manganate titrations, why can’t it be other acids

A

Dilute H2SO4 Must be used

Using a weak acid like ethanoic acid would not be able to supply the large amount of H+ ions needed

Can’t be conc Hcl as Cl- ions will be oxidised to cl2

Can’t be nitric acid as it is an oxidising agent and would oxidise Fe2+ to Fe3+

See chemrevise notes for details

36
Q

What is a heterogenous catalyst

A

It is in a different phase from reactants

Catalyst usually solid

37
Q

What is a homogenous catalyst

A

It is in the same phase as reactants, the reaction proceeds through an intermediate species

38
Q

How would strength of adsorption help determine effectiveness of catalyst?
Give 2 catalysts that are most useful in this sense

A

Some metals like W have too strong adsorption and so products cannot be released.
Metals like Ag have too weak adsorption so reactants do not adsorb in high enough concentration

Nickel and platinum have right strengths

39
Q

What’s the active site

A

The place where reactants adsorb (gather) on to the surface of the catalyst

40
Q

An example of heterogenous catalyst is in the contact process, which catalyst is used

A

V2O5

41
Q

What catalyst is used in Haber process

A

Iron

42
Q

Why can’t leaded petrol used in cars fitted with a catalytic converter

A

Lead strongly adsorbs (to gather) onto the surface of the catalyst

43
Q

Silver can form complexes and show catalytic behaviour, Why is it different from transition metals

A

It doesn’t form coloured compounds and does not have variable oxidation state.
Also doesn’t have incomplete d she’ll

44
Q

State the equation and colour change in the reaction between NaOH and Cr3+

A

Cr3+ -> Cr(OH)3 green ppt 🌳

Dissolved in excess to form [Cr(OH)6]3- dark green solution

45
Q

What is disproportionate

A

It is when the same element has been oxidised and reduced in the same reaction

46
Q

Colour of copper

A

Brown solid

47
Q

Colour of CuSo4

A

Blue solution

48
Q

What does amphoteric metals mean

Give an example

A

They can act as both acid and base

Al(OH)3(H2O)3 solid

49
Q

Why are metal 3+ ions more acidic

A

They are pretty small but have a big charge -> high charge density
Makes them more polarising meaning they attract electrons from oxygen more strongly
Weakening OH bond
More likely H+ release
More acidic

Chemistry (12 decks)

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