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Chemistry Year 12 > Transition metals 3.2.5 > Flashcards

Transition metals 3.2.5 Flashcards

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1
Q

what are the characteristics of transition metals because of their incomplete d sub shell

A
  • Formation of coloured ions
  • Variable oxidation states
  • Catalytic activity
  • Complex ion formation
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2
Q

why is Zn not a transition metal

A

Zn can only form a 2+ ion. In this ion the Zn2+ has a complete d orbital and so does not meet the criteria of having an incomplete d orbital in one of its ions

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3
Q

Why is Sc not a transition metal

A

Sc can only form a 3+ ion. In this ion the Sc3+ has an empty d orbital and so does not meet the criteria of having an incomplete d orbital in one of its ions

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4
Q

what’s the electron configuration of Zn

A

1s2 2s2 2p6 3s2 3p6 4s2 3d10

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5
Q

what’s the electron configuration of Zn2+

A

1s2 2s2 2p6 3s2 3p6 4s0 3d10

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6
Q

what’s the electron configuration of Sc3+

A

1s2 2s2 2p6 3s2 3p6 4s0 3d0

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7
Q

what’s the electron configuration of Sc

A

1s2 2s2 2p6 3s2 3p6 4s2 3d1

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8
Q

what do you have to do when working out the electron configuration of transition metal ions

A

When forming ions lose 4s before 3d

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9
Q

why do transition metals have variable oxidation states

A

This is because the electrons sit in 4s and 3d energy levels which are very close to

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10
Q

what is a complex

A

is a central metal ion surrounded by ligands

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11
Q

what is a ligand

A

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

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12
Q

what is coordinate bonding

A

When the shared pair of electrons in the covalent bond come from only one of the bonding atoms

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13
Q

what is co ordination number

A

The number of coordinate bonds formed to a central metal ion

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14
Q

what is a unidentate ligand

A

can form one coordinate bond per ligand eg. H2O , NH3 and Cl-

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15
Q

what is a bidentate ligand

A

Have two atoms with lone pairs and can form two coordinate bonds per ligand e.g NH2CH2CH2NH2 , ethanedioate ion , C2O4- , ethane-1,2-diamine

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16
Q

what is multidentate ligand

A

Can form 6 coordinate bonds per ligand e.g. EDTA4-

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17
Q

what is the shape dependent on

A

The size of the ligands and the coordination number

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18
Q

what shape does a complex with a coordination number of 6 form and what’s the bond angle

A

an octahedral shape
90 degrees

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19
Q

how many NH3 and H20 ligands can fit around a central metal ion

A

6 because they’re smaller in shape

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20
Q

how many Cl- ligands can you fit around a central metal ion

A

4 because they’re larger

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21
Q

How many ethanedioate and ethane - 1,2-diamine ligands can you fit around a central metal ion

A

3 because they’re large

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22
Q

what shape are complexes with a coordination number of 4 form and the bone angle

A

Tetrahedral
109.5 degrees
Square planar
90

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23
Q

what’s a specific example of a square planar complex

A

Cis-platin
Pt as central metal ion
2 Cl ligands around it
2 NH3 ligands around it

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24
Q

what shape does a complex with a coordination number of 2 have and the bond angle

A

Linear
180 degrees

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25
Q

what’s the specific example of a linear shape

A

[Ag(NH3)2]+
Tollens reagent

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26
Q

how do you work out the total oxidation state of the metal

A

Total oxidation state of the complex - total oxidation state of the ligands

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27
Q

what is haem

A

A multidentate ligand that is found in the molecule haemoglobin

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28
Q

what’s the shape of haemoglobin

A

Tetrahedral

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29
Q

How does haemoglobin transport oxygen

A

-oxygen substitutes the water ligand in the lungs where oxygen conc is high to form oxyhemoglobin which is then transported around the body
- Oxyhaemoglobin gives up oxygen to a place where it’s needed. Water takes the place and haemoglobin returns back to the lungs to start the process again

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30
Q

what happens when carbon monoxide is inhaled

A

The water ligand is replaced with a carbon monoxide ligand
carbon monoxide bonds strongly so it’s not readily replaced by oxygen or water

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31
Q

how do you know if you have a trans isomer

A

if the 2 different ligands are opposite each other

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32
Q

how do you know if you have a cis isomer

A

If the 2 different ligands are adjacent to each other

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33
Q

what is cisplatin

A

It’s used as an anti cancer drug
Platin binds to DNA of cancer cells and stops cancer dividing .
It can also prevent the replication of healthy cells by binding on to healthy DNA which may lead to unwanted side effects like hair loss

34
Q

when does the d sub shell split into 2

A

When ligands bond with the central metal ion

35
Q

what happens when the d sub shell is split into 2

A

An energy gap is created
When electrons absorb light energy some move from the lowest energy level ( ground state ) to higher energy level orbitals ( excited state)

36
Q

in order for the d subshell to enter a higher energy level what must happen

A

The energy from the light must equal delta E

37
Q

what is the size of delta E dependent on

A

•The central metal ion and its oxidation state
• the type of ligand
• the coordination number

38
Q

what’s the equation to work out energy absorbed by the electrons

A

delta E = hc / wavelength of light absorbed

h= plancks constant
c= speed of light

39
Q

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

A

The size of delta E
- the large the energy gap of delta E the higher the frequency of light absorbed

40
Q

what happens if any frequencies which are not absorbed

A

They are reflected or transmitted

41
Q

what’s the colour of the complexes where we have a full 3d or empty 3d subshell

A

Colourless or white
- No electrons can migrate to the higher energy level

42
Q

when does ligand substitution happen

A

the coordination number changes and so does the shape .
normally happens when a smaller ligand is substituted by a larger ligand

43
Q

what has an impact on the colour

A

The coordination number
The oxidation state

44
Q

what is colorimetry used to measure

A

the concentration of transition metal ions in solution

45
Q

what’s the reaction for a copper complex ion reacting with excess ammonia

A

[Cu(H20)6]2+ (aq) + 4NH3(aq) => [Cu(NH3)4(H2O)2] 2+ + 4H2O

46
Q

what’s the reaction of cobalt complex ion reacting with chlorine

A

[Co(H20)6]2+(aq) + 4Cl-(aq) => [CoCl4] 2- (aq) + 6H2O(l)

47
Q

what’s the reaction between copper complex ion and chlorine

A

[Cu(H20)6]2+(aq) + 4Cl-(aq) => [CuCl4] 2- (aq) + 6H2O(l)

48
Q

what’s the reaction between iron complex ion and chlorine

A

[Fe(H20)6]3+(aq) + 4Cl-(aq) => [FeCl4]- (aq) + 6H2O(l)

49
Q

which ligands are more stable

A

Multidentate ligands are more stable than moderate ligands

50
Q

when are the bonds broken and formed in a ligand substitution reaction

A

Bonds are broken in the original complex and new ones are formed to make the new complex

51
Q

what is the chelate effect

A

the increase in stability .
When we substitute monodentate ligands with bidentate ligands and multidentate ligands we create a solution with more particles in it . This means we have an increase in entropy => more likely
to happen

52
Q

what’s the colour of the 4 vanadium ions , v2+ , V3+ , VO2+ and Vo2 +

A

V2+
Violet
V3+
Green
VO2+
Blue
Vo2 +
yellow

53
Q

what’s the reaction for VO2+ reduced to Vo 2+

A

2Vo2 + (aq)+ Zn(s) + 4H+(aq) => 2VO2+ (aq) + Zn2+(aq) + 2H2O(l)
yellow to blue

54
Q

what’s the reaction of VO2+ reduced to V3+

A

2VO2+ (aq) + Zn(s). + 4H+ (aq) => 2V3+ (aq) + Zn2+(aq) + 2H2O(l)
Blue to green

55
Q

what’s the reaction of V3+ reduced to V2+

A

2V3+(aq) + Zn(s) => 2V2+(aq) + Zn2+(aq)
Green to violet

56
Q

what is used to reduce vanadium ions

A

zinc (zn)

57
Q

what does redox potentials tell us

A

How easily an ion is reduced

58
Q

what type of ions have the largest redox potentials

A

The least stable have the largest redox potentials and are likely to be reduced

59
Q

why might there be a difference in redox potentials to the standard values seen in a data book

A

Dependent on the environment the ions are in
Standard conditions :
100kPa
298K
1moldm-3

60
Q

what affects the redox potential

A
  • ligand
  • pH ( more acidic the solution is the larger the redox potential - more likely to be reduced )
61
Q

what’s the reaction for the oxidation of Fe3+ to Fe2+

A

MnO4-(aq) + 8H+(aq) + 5Fe2+(aq) => Mn2+ (aq) + 4H2O(l) + 5Fe3+(aq)
purple => colourless

62
Q

what’s the reaction for reducing Fe3+ to Fe2+

A

2Fe3+(aq) + 2I-(aq) => I2(aq) + 2Fe2+(aq)

63
Q

what’s the reaction for reducing Cr3+ to Cr2+

A

Cr2O72- + 14H+ + 6Fe2* => 2Cr3+ + 7H2O + 6Fe3+
Orange to green

64
Q

what is a heterogenous catalyst

A

Catalyst that is in a different phase from the reactants .
The catalyst is one different state to the reactants

65
Q

what’s an example of a heterogeneous catalyst

A

The haber process :
N2 + 3H2 => 2NH3
A solid iron catalyst is used

66
Q

what increases the rate of reaction of a heterogenous catalyst

A

increasing the surface area of a heterogeneous catalyst increases the rate of reaction

67
Q

what’s a homogenous catalyst

A

catalyst that’s in the same phase as the reactants.
They form intermediate species by reactants combining with the catalyst which react to form products
Catalyst is reformed again

68
Q

what is the contact process

A

uses vanadium (V) ( V2O5) to make sulfuric acid ( SO2 to SO3)

69
Q

what are the reactions of the contact process

A

1) V2O5 + SO2 => V2O4 + SO3
2) V2O4 + 1/2O2 => V2O5

70
Q

what kind of catalysts are used in the contact process

A

heterogenous catalyst

71
Q

what’s a problem with using heterogeneous catalysts

A

Can be poisoned by impurities :
Impurities can bind to the surface of a catalyst and can block active sites for reactants to adsorb.
When an impurity blocks a site it’s called poisioning
Catalytic poisoning reduced the surface area of the catalyst for the reactants to add on to.
This slows down the reaction

72
Q

what does a poisoned catalyst mean

A
  • less product is made
  • the catalyst needs to be replaced or cleaned more often
  • increased cost of all chemical process
73
Q

how many activation energies does a homogenous catalyst have

A

2

74
Q

what’s an example of using homogeneous catalysts

A

Fe2+ oxidised to Fe3+
S2O8 reduced to SO42-

75
Q

how do we speed up reactions using a homogeneous catalyst

A

lowering the activation energy

76
Q

what is autocatalysis

A

another form of homogenous catalysis where the product catalysises the reaction

77
Q

what is an example of autocatalysis

A

where Mn2+ is the catalyst in a reaction between C2O42- and MnO4-

78
Q

EQ : state the meaning of the term transition metal complex (1)

A

metal atom / ion surrounded by ligands

79
Q

EQ : why is this reaction slow before catalyst is added

A

Two negative ions repel so activation energy is high

80
Q

what is the electron configuration of an atom of a transition metal

A

4s2 3d8

Chemistry Year 12 (24 decks)

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