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Edexcel A Level Chemistry > ✅15 - Transition Metals > Flashcards

✅15 - Transition Metals Flashcards

1
Q

Where are transition metals found in the periodic table?

A

D block

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2
Q

What are transition metals?

A

D block elements that can form one or more stable ions with incompletely filled d-orbitals

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3
Q

Which d block period 4 elements are not transition metals?

A

Scandium and Zinc

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4
Q

How many electrons can the d orbital hold?

A

10

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5
Q

When ions are formed, which electrons are removed first?

A

The s electrons

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6
Q

Why is Scandium not a transition metal?

A

It only forms one ion, Sc3+, which has an empty d subshell

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7
Q

Why is zinc not a transition metal?

A

It only forms one ion, Zn2+, which has a full d subshell

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8
Q

How many stable oxidation states does Vanadium have?

A

4

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9
Q

What are the stable oxidation states of Vanadium?

A

II, III, IV, V

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10
Q

What do transition metals have?

A

Variable oxidation states

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11
Q

What conditions must be met to form a compound of complex with an ion of a certain oxidation number?

A

The energy given out when the ion forms a compound or complex needs to be greater than the ionisation energy

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12
Q

How do transition metals form ions?

A

By loosing electrons from their 4s and 3d subshells

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13
Q

When does the energy released when an ion forms a complex or compound increase?

A

When the ionic charge increases.

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14
Q

What are complex ions?

A

Metal ions surrounded by datively covalently bonded ligands

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15
Q

What is a ligand?

A

An atom, ion or molecule which donates a pair of electrons to a central metal atom or ion.

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16
Q

What are monodentate ligands?

A

Ligands with one lone pair

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17
Q

What are bidentate ligands?

A

Ligands with two lone pairs

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18
Q

What are multidentate ligands?

A

Ligands with more than two lone pairs

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19
Q

What are examples of monodentate ligands?

A

H2O, NH3, Cl-

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20
Q

What is an example of a multidentate ligands?

A

EDTA 4-

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21
Q

What is the name for water in a complex?

A

Aqua

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22
Q

What is the name for a hydroide group in a complex?

A

hydroxo

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23
Q

What is the name for ammonia in a complex?

A

Ammine

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24
Q

What is the name for chloride in a complex?

A

Chloro

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25
Q

How many colours traditionally make up white light?

A

7

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26
Q

Why are transition metal complexes coloured?

A

Electrons split into two energy levels when ligands attach. If an electron absorbs light, it can move to a higher energy level, and the light reflected is the colour seen

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27
Q

With 6 ligands, what shape is a complex?

A

Octahedral

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28
Q

With 4 ligands, what shape is a complex?

A

Tetrahedral or square planar

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29
Q

With 2 ligands, what shape is a complex?

A

Linear

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30
Q

What is an example of a linear complex?

A

Tollen’s reagent

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31
Q

What is cis-platin?

A

An anti-cancer drug which has a square planar shape

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32
Q

What does a cis- prefix indicate?

A

That the identical ligands are next to each other

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33
Q

What does a trans- prefix indicate?

A

That the identical ligands are opposite each other

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34
Q

How does cis-platin kill cancer cells?

A

It forms a bond between the two strands of DNA which prevents them from separating, and therefore prevents replication

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35
Q

How is trans-platin different to cis-platin?

A

It is toxic and much less effective at targeting cancer

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36
Q

Why does reducing the number of ligands increase stability?

A

The system becomes more disordered and there is an increase in ∆S system

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37
Q

What causes the greatest increase in stability?

A

Exchanging a monodentate ligand for a multidentate ligand

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38
Q

How is Fe held in haemoglobin?

A

By forming dative bonds with four nitrogens in the structure, in a square planar

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39
Q

What else is bonded to the Fe in haemoglobin?

A

Globin (a protein) and Oxygen

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40
Q

Why is carbon monoxide poisonous?

A

Because the dative bond between carbon monoxide and haemoglobin is stronger than with oxygen, so any CO breathed in will bins with the haemoglobin and not break easily

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41
Q

What is the equation for the reaction between aqueous NaOH and copper(II) sulfate solution?

A

[Cu(H2O)6]2+ + 2OH- —> [Cu(H2O)4(OH)2] + H2O

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42
Q

What colour is [Cu(H2O)4(OH)2]?

A

Blue precipitate

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43
Q

What is the equation for the reaction between aqueous ammonia and copper (II) sulfate?

A

[Cu(H2O)6]2+ + NH3 —-> [Cu(H2O)4(OH)2] + 2NH4+

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44
Q

What is the equation for the reaction between the blue copper precipitate and aqueous ammonia?

A

[Cu(H2O)4(OH)2] + 4NH3 —-> [Cu(NH3)4(H2O)2]2+ + 2H2O + 2OH-

45
Q

What colour is [Cu(NH3)4(H2O)2]2+?

A

Deep blue solution

46
Q

What is the equation for the reaction between copper (II) sulfate solution and conc HCl?

A

{CU(H2O)6]2+ + 4Cl —-> [CuCl4]2- + 6H2O

47
Q

What is the colour change when hydrochloric acid is added to copper sulfate solution?

A

Blue to green to yellow

48
Q

What is the equation for the reaction between hexaaquacobalt(II) and aqueous sodium hydroxide?

A

[Co(H2O)6]2+ + 2OH- —-> [Co(H2O)4(OH)2] + 2H2O

49
Q

What is the colour change when sodium hydroxide is added to hexaaquacobalt(II)?

A

Pink solution to blue precipitate

50
Q

How many reactions occur between hexaaquacobalt(II) and ammonia?

51
Q

What is the acid-base reaction between hexaaquacobalt(II) and NH3?

A

[Co(H2O)6]2+ + 2NH3 —-> [Co(H2O)4(OH)2] + 2NH4+

52
Q

What is the equation for the reaction between [Co(H2O)4(OH)2] and NH3?

A

[Co(H2O)4(OH)2] + 6NH3 —-> [Co(NH3)6]2+ + 4H2O + 2OH-

53
Q

What is the colour change between hexaaquacobalt(II) and ammonia?

A

Precipitate dissolves to a brown solution

54
Q

What is the colour od the [Co(NH3)6]3+ ion?

55
Q

What is the equation for the reaction between hexaaquacobalt(II) and conc HCl?

A

[Co(H2O)6]2+ + 4Cl- —-> [CoCl4]2- + 6H2O

56
Q

What is the colour change when conc HCl is added to the hexaaquacobalt (II) solution?

A

Pink to blue

57
Q

What is the equation for the reaction between hexaaquairon(II) and sodium hydroxide?

A

[Fe(H2O)6]2+ + 2OH- —-> [Fe(H2O)4(OH)2] + 2H2O

58
Q

What is the colour change in the reaction between hexaaquairon(II) and sodium hydroxide?

A

Pale green solution forms a green precipitate

59
Q

What is the equation for the reaction between hexaaquairon(II) and NH3?

A

[Fe(H2O)6]2+ + 2NH3 —-> [Fe(H2O)4(OH)2] + 2NH4+

60
Q

What is the equation for the reaction between hexaaquairon(III) and sodium hydroxide?

A

[Fe(H2O)6]3+ + 3OH- —-> [Fe(H2O)3(OH)3] + 3H2O

61
Q

What is the colour change for the reaction between hexaaquairon(III) and sodium hydroxide?

A

Yellow-brown solution forms and brown precipitate

62
Q

What is the equation for the reaction between hexaaquairon(III) and NH3?

A

[Fe(H2O)6] + 3NH3 —-> [Fe(H2O)3(OH)3] + 3NH4

63
Q

What are the colours shown by chromium compounds affected by?

A

Some compounds have different colours as solids and aqueous solutions
The colour of the solution depends on the concentration
The presence of dissolved oxygen in an aqueous solution can affect the colour seen

64
Q

What is the equation for the reaction between the hexaaquachromium(III) ion and aqueous sodium hydroxide?

A

[Cr(H2O)6]3+ + 3OH- —-> [Cr(H2O)3(OH)3] + 3H2O

65
Q

What is the colour change for the reaction between hexaaquachromium(III) and sodium hydroxide?

A

Green or violet solutions forms a green precipitate

66
Q

What is the equation for the reaction between hexaaquachromium(III) and NH3?

A

[Cr(H2O)6]3+ + 3NH3 —-> [Cr(H2O)3(OH)3] + 3NH4+

67
Q

What happens to the precipitate [Cr(H2O)3(OH)3] when it is dissolved?

A

It dissolves to form a green solution of [Cr(H2O)2(OH)4]-

68
Q

What happens to the precipitate [Cr(H2O)3(OH)3] when excess ammonia is added?

A

It is slow to dissolve but eventually a violet or purple solution of [Cr(NH3)6]3+ forms

69
Q

What is the equation for the reaction between [Cr(OH)6]3- and hydrogen peroxide?

A

2[Cr(OH)6]3- + 3H2O2 —-> 2CrO42- + 2OH- + 8H2O

70
Q

What is the colour change for the reaction between the chromium complex and hydrogen peroxide?

A

Green solution to yellow solution

71
Q

What is hydrogen peroxide?

A

An oxidising agent

72
Q

How does the chromate ion change with acidity?

A

In alkaline solution, the chromate(VI) ions are stable, but in acidic solution the dichromate(VI) are most stable

73
Q

What colour change is seen if acid is added to chromate ions?

A

Yellow to orange

74
Q

What can dichromate(VI) ions be reduced by?

75
Q

What is the equation for the reduction of dichromate ions using zinc?

A

Cr2O72- + 14H+ +3Zn —-> 2Cr3+ + 7H2O + 3Zn2+

76
Q

What is the colour change when dichromate ions are reduced?

A

Orange to green

77
Q

What is the colour change when Cr3+ is reduced to Cr2+?

A

Green to blue

78
Q

What reaction happens when NaOH is added to [Cr(H2O)3(OH)3]?

A

It forms [Cr(OH)6]3-

79
Q

What colour are V2+ ions?

80
Q

What colour are V3+ ions?

81
Q

What colour are (VO)2+ ions?

82
Q

What colour are (VO2)+ ions?

83
Q

In what compound does vanadium have a +4 oxidation number?

84
Q

In what compound does vanadium have a +5 oxidation number?

85
Q

Why is it easy to demonstrate a change in oxidation number with vanadium?

A

Because its colour changes are so distinctive

86
Q

What can be used to reduce vanadium from +5 to +2?

87
Q

What is the equation for the reduction of vanadium from +5 to +4?

A

2(VO2)+ + 4H+ + Zn —-> 2(VO)2+ + Zn2+ + 2H2O

88
Q

What is the equation for the reduction of vanadium from +4 to +3?

A

2(VO)2+ + 4H+ + Zn —-> 2V3+ + Zn2+ + 2H2O

89
Q

What is the equation for the reduction of vanadium from +3 to +2?

A

2V3+ + Zn —-> 2V2+ + Zn2+

90
Q

What is the equation for the reduction of vanadium from +2 to 0?

A

2V2+ + Zn —-> 2V + Zn2+

91
Q

Which of the vanadium reductions is not thermodynamically feasible?

92
Q

In what state are transition metals usually used as catalysts?

A

Solid, as a powder

93
Q

What is the catalyst in the contact process?

A

V2O5 - Vanadium Pentoxide

94
Q

What are the steps of surface adsorption theory?

A

Adsorption
Reaction
Desorption

95
Q

What is adsorption?

A

One or more reactants become attached to the catalyst

96
Q

What is the reaction step in surface adsorption theory?

A

Following the weakening of the bonds in the adsorbed reactants

97
Q

What is desorption?

A

The reaction product becomes detached from the surface of the catalyst

98
Q

What are the reactions that occur on the surface of vanadium in the contact process?

A

V2O5 + SO2 —-> V2O4 + SO3

V2O4 + 0.5O2 —-> V2O5

99
Q

What are the problems tackled by catalytic converters?

A

Increased pollution levels
Carbon monoxide emissions
Nitrogen monoxide emissions

100
Q

What are the transition metals used in catalytic converters?

A

Platinum and rhodium, sometimes palladium

101
Q

What is the equation for the reaction between Carbon monoxide and nitrogen monoxide?

A

2CO + 2NO —-> 2CO2 + N2

102
Q

Why does the reaction between CO and NO occur on catalytic converters?

A

Because the molecules of CO and NO are adsorbed and then, because their bonds are weakened, they react together to form CO2 and N2, which are then desorbed

103
Q

What is a key feature of homogeneous catalysts?

A

The formation of an intermediate species for which a specific formula can be written

104
Q

What is the equation for the reaction between persulfate ions and iodide ions?

A

S2O82- + 2I- —-> 2SO42- + I2

105
Q

What is the catalyst in the reaction between iodide and persulfate ions?

106
Q

What are the steps in the reaction between I- and S2O82-?

A

S2O82- and 2Fe2+ react together to form 2SO42- and 2Fe3+

2Fe3+ react with 2I- to form 2Fe2+ and I2

107
Q

Why do the Fe2+ and S2O82- react together?

A

Because they do not repel each other, as they have the opposite charge

108
Q

What is the alternative mechanism for the reaction between I- and S2O82-?

A

2Fe3+ + 2I- —-> 2Fe2+ + I2

S2O82- + 2Fe2+ —-> 2SO42- + 2Fe3+

Edexcel A Level Chemistry (20 decks)

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