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AQA A level Chemistry > Transition metals > Flashcards

Transition metals Flashcards

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1
Q

what is meant by a transition metal

A

A transition metal is a d-block element that can form at least one stable ion with an incomplete d sub-shell

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2
Q

What are the 4 characteristics of transition metals

A
  • complex formation
  • formation of coloured ions
  • variable oxidation state
  • catalyts
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3
Q

What colour complex is vanadium 2+ in solution

A

violet

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4
Q

What colour is vanadium 3+ in solution

A

green

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5
Q

What colour complex does vO 2+

A

blue

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6
Q

What colour does VO2 + form

A

Yellow

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7
Q

What are the trends in oxidation states

A
  • Relative stability of +2 state with respect to +3 state increases across the period
  • Compounds with high oxidation states tend to be oxidising agents e.g MnO4 -
  • Compounds with low oxidation states are often reducing agents e.g V2+ & Fe2+
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8
Q

What metal can reduce transition metals from a higher oxidation state to a lower oxidation state

A

Zinc

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9
Q

What colour does chromium three plus make

A

green/violet

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10
Q

What colour is Cr2O72-

A

orange

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11
Q

What colour is Mn 2+

A

Pink

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12
Q

What colour is MNO4 2-

A

Purple

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13
Q

Why are scandium and zinc not transition metals

A

they have a full d outer sub shell

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14
Q

What colour is Fe2+

A

Pale green

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15
Q

What colour does Fe 3+ form

A

Yellow

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16
Q

What colour is Co 2+

A

Pink

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17
Q

What colour is Cu 2+

A

Blue

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18
Q

State what is meant by a complex metal

A

:is a central metal ion surrounded by ligand linked by coordinate bonds

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19
Q

State what is meant by a ligand

A

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

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20
Q

State what is meant by co-ordination number

A

the number of co-ordinate bonds in a complex

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21
Q

What is a monodentate ligand and give examples of one

A

a ligand that can form one co-ordinate bond per ligand

Examples are water, ammonia, cl-

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22
Q

What is a bidentate ligand and examples

A

two atoms with lone pairs and can form two coordinate bonds per ligand

examples are: Ethabedioate, ethane-1-2, diamine

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23
Q

What is a multidentate ligand and give examples

A

which can form six coordinate bonds per ligand

examples is EDTA

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24
Q

What determines the shape of a complex

A

size of ligands

co-ordination number

25
Q

What shape do complexes with a co-ordination number of 6 form

A

octahedral shape

26
Q

What kind of isomerism do complexes show

A

Cis and trans

27
Q

Some octahedral complexes can form optical isomers

what types of ligands do these complexes have

A

3 bidentate ligands can form two optical isomers

28
Q

What shape do complexes with a coordination number of 4 form

A

Tetrahedral or square planar

example of tetrahedral is cucl4

the only square planar one you have to know is CisPlatin

29
Q

What shape do complexes with a coordination number of 2 form

A

Linear

example is tollens reagent

30
Q

What happens when

[Co(H2O)6]2+ reacts with 6 ammonia molecules

A

Forms

[Co(H2O)6]2+ (aq) + 6NH3 (aq) →[Co(NH3 )6]2+ (aq) + 6H2O (l)

Pink to yellow

The ligands NH3 and H2O are similar in size and are uncharged, so exchange occurs without change of co-ordination number

31
Q

what happens when [Cu(H2O)6]2+ reacts with ammonia

A

There is a partial substitution

[Cu(H2O)6]2+ (aq) + 4NH3 (aq)  [Cu(NH3 )4 (H2O)2]2+ (aq) + 4H2O (l)

colour change: blue to deep blue

Reacts with excess ammonia

32
Q

What happens when [Cu(H2O)6]2+ reacts with chloride

A

[Cu(H2O)6]2+ + 4Cl → [CuCl4]2- + 6H2O

The Colour change is blue to green/yellow

co-ordination number changes from 6 to 4 because Cl- is a bigger ligand

33
Q

What happens when [Co(H2O)6]2+ reacts with chloride

A

[Co(H2O)6]2+ + 4Cl → [CoCl4]2- + 6H2O

The Colour change is pink to blue

co-ordination number changes from 6 to 4 because Cl- is a bigger ligand

34
Q

What happens when [Fe(H2O)6]3+ reacts with 4 chloride ions

A

[Fe(H2O)6]3+ + 4Cl → [FeCl4]- + 6H2O

The Colour change is yellow to yellow

co-ordination number changes from 6 to 4 because Cl- is a bigger ligand

35
Q

Why can’t the reaction between [Fe(H20)6]3+ and cyanide ions not be easily reversed

A

because the cyanide ligand forms a stronger bond to the iron

36
Q

How does human haemoglobin transport oxygen

A
  • oxygen substitutes the water ligand in the lungs
  • this forms oxyhaemglobin, this the deposit water at oxygen and picks up water instead
37
Q

What is the effect of carbon monoxide on haemoglobin

A
  • Carbon monoxide is inhaled carbon monoxide replaces the water ligand
  • carbon monoxide bonds strongly to haemoglobin
  • thsi means oxygen won’t be picked up
38
Q

What is the chelate effect

A

When a monodentate lighand is substituted of with a bidentate or a multidentate ligand leads to a more stable complex

39
Q

What happens to orbitals when a ligand is added to it

A

they go through d-orbital splitting, where two orbitals are in a higher energy level and three are in a lower energy level

40
Q

Explain why complexes with a partially filled d subshell can form coloured complexes

A

-The electrons can now move to a higher energy level (from ground state to the excited state because they have been exited,

due to absorbing visible light

the light that is not absorbed is transmitted to give the substance colour

41
Q

ΔE = hv or ΔE = hc/λ

above is the equation for delta E (energy gap) what does each symbol mean

A

v = frequency of light absorbed (unit s-1 or Hz)

H = Planck’s constant 6.63 × 10–34 (J s)

E = energy difference between split orbitals (J)

c = speed of light 3.00 x 108 (m s–1 )

λ = wavelength of light absorbed (m)

42
Q

What is delta E and is the size of delta e dependent on

A

energy gap

  1. Dependent on the central atom and oxidation tate
  2. type of ligand
  3. co-ordination number
43
Q

Why do some complexes produce colourless or white

A

because those complexes gave full or empty three-d sub shell, so no electrons can migrate to a higher energy level

44
Q

What can affect the redox potential of transition metals

A

if they are not done in standard conditions

45
Q

The more acidic the solution the more …… the electrode potential

A

larger the electrode potential which means it easily reduced

46
Q

What are the two types of catalyst

A

Heterogenous and homogenous

47
Q

What happens to vandium 5+ in acidic solution if you add zinc

A

will reduce the vanadium down through each successive oxidation state,

and the colour would change from yellow to blue to green to violet.

48
Q

State what is meant by a heterogenous catalyst

A

heterogeneous catalyst is in a different phase from the reactants

49
Q

State what is meant by a homogenous catalyst

A

homogeneous catalyst is in the same phase as the reactants

50
Q

How do heterogeneous catalysts work

A
  1. Reactants adsorb into the surface (in mark schemes) by forming bonds with atoms at active sites on the catalyst’s surface
  2. bonds in the reactants are weakened and break or a reaction happens
  3. the product desorbs of the surface of the catalyst
51
Q

How is vanadium used in the contact process, give the overall and step equations

A

Overall equation : 2SO2 + O2 → 2SO3

step 1 SO2 + V2O5→ SO3 + V2O4

step 2: 2V2O4 + ½ O2 → 2V2O5

52
Q

What is the name of the catalyst used in the Haber process

A

Iron

53
Q

What is meant by the phrase poising catalysts?

A

when poisoned by impurities and which reduces efficiency

this means that less product is made, catalyst needs to be replaced or cleaned,

54
Q

How do homogenous catalysts work

A

-form an intermediate

55
Q

What’s different about homogenous energy profiles

A

they have two activation energies

56
Q

How do homogenous catalysts work with S2o8 and I-

A

s2o8 2- + 2Fe2+ → 2Fe3+ + 2so4 2-

2fe3+ + 2I- → I2 + 2Fe2+

Fe2+ is refomed

57
Q

What is autocatalysis

A

another form of homogenous catalysts where the product catalyses the reaction

58
Q

What is an example of autocatalysis

A

Mn2+

2MnO4- + 16h+ + 5C2O42- → 2Mn2+ + 8H20 + 10Co2

then

Mn2+ + Mno4- + 8H+ → 2Mn3+ + 4H2o

then

2Mn3+ c2O42- + 2Mn 2+ + 2Co2

AQA A level Chemistry (26 decks)

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