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Chemistry A2 Rafa > 5.3 Transition metals > Flashcards

5.3 Transition metals Flashcards

1
Q

What is a transition element (metal)?

A

a d-block element that has an incomplete d-sub-shell as a stable ion

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2
Q

Which d-block elements are not transition metals and why?

A
  • scandium and zinc

- they do no have ions with partially filled d-orbitals

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3
Q

Which elements have irregular orbital filling patterns?

A

CHROMIUM - the five 3d-orbitals and the 4s orbital all contain one electron
COPPER - the five 3d orbitals are full, there is only one electron in the 4s orbital

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4
Q

Which electrons do transition element ions lose first?

A

4s before 3d because, once electrons occupy the orbitals, the 4s electrons have a higher energy and are lost first

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5
Q

Physical properties of transition metals

A
  • lustrous in appearance
  • high densities
  • high melting and boiling points
  • can conduct electricity
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6
Q

Chemical properties of transition metals

A
  • different oxidation states
  • form coloured solutions when dissolved in water
  • often used as catalysts
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7
Q

Are transition metals powerful reducing or oxidising agents?

A

oxidising

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8
Q

Example of disproportiation reaction of transition metal

A

adding hot dilute sulphuric acid to copper (I) oxide we form blue solution of Cu (II) sulphate and brown precipitate of copper solid
Cu2O + H2SO4 = Cu + CuSO4 + H2O

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9
Q

Why are different colours associated with transition metals?

A

movement of electrons in partially filled d-orbitals

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10
Q

Two ways transition metals act as catalysts

A
  • provide a surface for reaction to take place (atoms absorb onto surface and held in place)
  • can change their oxidation states (bind to reactants and form intermediates)
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11
Q

Disadvantages of using transition metals as catalysts in industry

A
  • can be toxic or damaging to environment

- must be disposed of carefully

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12
Q

Describe Haber process reaction and catalyst

A 
N2 + 3H2 = 2NH3
iron metal (increases rate and lower temp)
ammonia used for agricultural fetilisers
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13
Q

Describe contact process reaction and catalyst

A

2SO2(g) + O2(g) = 2SO3 (g)

vanadium (V) oxide, V2O5

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14
Q

What is SO3 from the contact process used for?

A

To manufacture sulfuric acid which is use for:

  • fertilisers
  • detergents
  • adhesives
  • explosives
  • electrolyte in car batteries
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15
Q

Describe decomposition of hydrogen peroxide and catalyst

A

2H2O2 = 2H2O +O2

manganese (IV) oxide, MnO2

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16
Q

What is decomposition of hydrogen peroxide used for?

A

preparation of oxygen gas

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17
Q

Describe hydrogen production and catalyst

A

Zn(s) + H2SO4(aq) = ZnSO4(aq) + H2 (g)

CuSO4 catalyst`

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18
Q

What is a complex ion?

A

a transition metal ion bonded to one or more ligands by coordinate (dative covalent bonds)

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19
Q

What is a ligand?

A

a molecule or ion that can donate a pair of electrons to the transition metal ion to form a coordinate bond

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20
Q

What is the coordination number?

A

the total number of coordinate bonds formed between a central metal ion and its ligands

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21
Q

When are complex ions formed?

A

When transition metal compounds are present in a solution

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22
Q

What is a monodentate ligand?

A

the ligand donates just one pair of electrons to the central metal ion to form one coordinate bond

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23
Q

What monodentate Ligands do we need to know?

A

OH2 (water)
NH3 (ammonia)
Chloride Cl-

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24
Q

What are bidentate ligands?

A

have two pairs of electrons from different atoms to donate to the central metal so two coordinate bonds can form

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25
Q

What is the most common bidentate ligand and what is it shortened to?

A

ethane-1,2-diamine, NH2CH2CH2NH2
shortened to ‘en’
each nitrogen donates a lone pair

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26
Q

How many coordinate bonds does a octahedral complex have and what are the bond angles?

A

6

90 or 180

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27
Q

Why can only four chloride ligands fit around the metal ion?

A

they are big

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28
Q

What complexes do chloride ions form?

A

tetrahedral

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29
Q

What is a square planar complex?

A

Where four monodentate ligands arrange themselves in the same plane at the metal atom

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30
Q

Define stereoisomerism

A

species with them same structural formula but with a different arrangement of atoms in space

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31
Q

What are the two types of stereoisomerism in transitional element chemistry?

A

cis-trans isomerism

optical isomerism

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32
Q

Colour of Cu2+ in solution

33
Q

Colour of Fe2+ in solution

34
Q

Colour of Fe3+ in solution

35
Q

Colour of Mn2+ in solution

36
Q

Colour of Cr3+ in solution

A

Violet (often green)

37
Q

Colour of Cu2+ after addition of NaOH/NH3

A

Blue ppt (Cu(OH)2)

38
Q

Colour of Fe2+ after addition of NaOH/NH3

A

Green ppt. Fe(OH)2

39
Q

Colour of Fe3+ after addition of NaOH/NH3

A

Brown ppt. Fe(OH)3

40
Q

Colour of Mn2+ after addition of NaOH/NH3

A

Brown ppt. Mn(OH)2

41
Q

Colour of Cr3+ after addition of NaOH/NH3

A

Green grey ppt. Cr(OH)3

42
Q

`Colour of Cr3+ after addition of excess NaOH

A

Green sol. [Cr(OH6)]3-

43
Q

Colour of Cu2+ after addition of excess NH3

A

Dark blue sol. [Cu(H2O)2(NH3)4]2+

44
Q

Colour of Cr3+ after adding excess NH3

A

Purple sol. [Cr(NH3)6]3+

45
Q

What is ligand substitution?

A

reaction in which one ligand in a complex ion is replaced by another ligand

46
Q

`What does an aqueous solution of Cu2+ ions form?

A

[Cu(H2O)6]2+ complex ions

47
Q

What colour are [Cu(H2O)6]2+ ions?

48
Q

What is the colour change when [Cu(H2O)6]2+ is added to NH3?

A

blue to deep blue

49
Q

Equation for the reaction between aqueous Cu2+ ions and NH3

A

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

50
Q

Two observations shown when carrying out the reaction between Cu2+ and ammonia experimentally

A

1) blue ppt of Cu(OH)2 forms (small amount of ammonia)

2) deep blue solution formed with excess ammonia

51
Q

Colour change when HCl is added to Cu2+?

A

pale blue to green to yellow

52
Q

How do you reverse the reaction between HCl and Cu2+?

A

By adding water

53
Q

Equilibrium between Cu2+ and HCl reaction

A

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

54
Q

Why does [Cu(H2O)6]2+(aq) have 6 ligands but [CuCl4]2-(aq) only has four?

A

Chloride ligands are larger than water ligands and have stronger repulsion

55
Q

Equation for the reaction between chromium (III) and excess ammonia

A

[Cr(H2O)6]3+ +6NH3 = [Cr(NH3)6]3+ +6H2O

56
Q

What ions does aqueous solution of chromium (III) contain?

A

[Cr(H2O)6]3+

57
Q

[Cr(H2O)6]3+ colour

58
Q

Colour change of reaction between chromium (III) and excess ammonia

A

violet to purple

59
Q

Describe the coordinate bonds on Fe2+ in haem

A
  • four coordinate bonds between Fe2+ and nitrogen
  • one coordinate to globin protein
  • final coordinate bonds to O2
60
Q

Why is CO dangerous?

A

It binds more strongly to haem the O2

Not reversible

61
Q

What are the three typical reactions of transition metals?

A

Precipitation
Ligand substitution
Redox

62
Q

What two species do we need to know the ligand substitution reactions of?

A

[Cr(H2O)6]3+

[Cu(H2O)6]2+

63
Q

Example of a precipitation reaction

A

Cu2+ + 2OH- = Cu(OH)2

64
Q

Four redox reactions that we need to know

A

Fe2+ = Fe3+ + e-
2Cr3+ +7H2O = Cr2O72- + 14H+ +6e-
Cu2+ + e- = CuI + I2
Cu+ = Cu + Cu2+

65
Q

What is needed for Fe2+ = Fe3+ + e-?

66
Q

What is needed for Fe3+ + e- = Fe2+ ?

67
Q

What is needed for 2Cr3+ +7H2O = Cr2O72- + 14H+ +6e-?

68
Q

What is needed for Cr2O72- + 14H+ +6e- = 2Cr3+ +7H2O?

69
Q

What is needed for Cu2+ + e- = CuI + I2

70
Q

What colour is CuI?

A

White precipitate

71
Q

What colour is I2 and state?

A

brown/yellow solid

72
Q

What colour is Cu+?

A

light brown/ yellow solid

73
Q

What colour is Cu metal?

A

red/orange

74
Q

Example of octahedral complex ion?

A

[Cu(H2O)6]2+

[Fe(H2O)6]3+

75
Q

Example of tetrahedral complex ion?

A

[CuCl4]2–

[CoCl4]2–

76
Q

Example of square planar complex ion?

A

Pt(NH3)2Cl2

77
Q

Requirements for optical isomerism of transition elements

A
  • three bidentates
  • two bidentates and two monodentates
  • one hexadentate ligand
78
Q

What is cis-platin?

A

Anti-cancer drug
PtCl2(NH3)2
Binds to DNA of cancer cells to prevent cell division

79
Q

Benefits and risks of cis-platin

A

Benefits of chemotherapy

Unpleasant side effects

Chemistry A2 Rafa (8 decks)

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