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Edexcel Chemistry A level > Transition metal > Flashcards

Transition metal Flashcards

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1
Q

define Ligand

A
  • an ion, atom or molecule that can donate an electron.
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2
Q

Give 4 characteristics of transition metals

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

What does dentate mean

A
  • the number of coordinate bond per ligand
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4
Q

Give 4 examples of monodentate ligands

A
  • H20
  • NH3
  • Cl-
  • OH-
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5
Q

Describe the function of haemoglobin

A
  • protein used to transport oxygen around the body in blood
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6
Q

Name the shape of the haemoglobin molecule

A
  • octahedral
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7
Q

Describe the structure of Haemoglobin

A
  • central Fe2+ ion
  • 4 nitrogen multidendate ligands
  • oxygen/water that coordinate bonds with the Nitrogen to allow transport of molecules around the body
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8
Q

Describe the action of haemoglobin in the lungs, and back.

A
  • lungs: oxygen subs in the water ligand where oxygen conc is high to form oxyhaemoglobin.
  • oxyhaemoglobin gives up oxygen to a place where it’s needed, and water subs in again, taking back haemoglobin to the lungs to start over.
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9
Q

Explain why CO is a poisonous gas

A
  • the water ligand will be replaced with CO ligand
  • CO has higher bonding affinity to haemoglobin, so not readily replaced oxygen
  • so O2 can’t be transported, leading to oxygen starvation
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10
Q

what type of octahedral complexes will show optical isomerism?

A
  • with 3 bidentate ligands
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11
Q

When will octahedral complex ions show cis/trans isomerism

A
  • Octahedral complexes with 4 ligands and the SAME type of 2 ligands of a different display.
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12
Q

When will it be considered a trans isomer?

A
  • when the 2 different ligands are opposite to each other
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13
Q

When will the complex ions show cis isomerism?

A
  • when the 2 different ligands are adjacent to each other.
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14
Q

When will square planar complex ions show cis/trans isomerism?

A
  • when they have 2 ligands of the same type and 2 ligands of a different type.
    (basically, 2 Cl and 2 NH3 for eg)
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15
Q

What happens to the d orbital when ligands bond with the central metal ion?

A
  • split into 2
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16
Q

describe what happens when ligands bond with central metal ions

A
  • d-subshell splits
  • some orbitals gain energy, creating an energy gap.
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17
Q

Describe why transition metal complexes are coloured.

A
  • ligand causes d orbitals to split into 2
  • Electrons absorb energy
  • so electrons get excited, and are promoted to higher d orbitals
  • the unabsorbed light is seen as the complementary colour.
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18
Q

In what situation will a colour not be seen?
why?

A
  • complexes that have a completely full or empty 3d subshell.
  • because it means that no electrons can migrate to the higher energy level.
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19
Q

What is the relationship between the frequency and energy gap.

A
  • the larger the gap, the higher the frequency of light (eg purple - blue range of visible light)
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20
Q

What is the colour of a transition metal dependant on? (3)

A
  • type of ligand
  • shape of the ligand
  • oxidation state of the central metal ion
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21
Q

What does the frequency absorbed depend on?

A

the size of the energy gap.

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22
Q

What happens to the frequencies that are not absorbed?

A
  • reflected or transmitted.
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23
Q

What characterises a transition element?

A
  • a d-block element that can form at least one stable ion with a partially filled d-subshell
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24
Q

describe the electron configuration principle for transition elements.

A
  • fill up singly first, then double up.
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25
Q

Why is scandium not a transition element?

A
  • its ION, Sc3+ has an empty d-subshell
  • so since its not partially filled, it is not a transition element.
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26
Q

Why is zinc not a transition element?

A
  • its ion, Zn2+ has a full d-subshell.
  • Its partially filled, so not transition element.
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27
Q

What is the rule for forming ions with transition metals?

A
  • loose electrons from 4s first, then 3d orbital.
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28
Q

Colour of V2+ in solution

A

violet

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29
Q

Colour of V3+ in solution

A

green

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30
Q

Colour of VO(2+) in solution

A

Blue

31
Q

Colour of V(O2)+ in solution

A

yellow

32
Q

Colour of Cr3+ in solution

A

green/violet

33
Q

Colour of Cr2O72+ in solution

A

orange

34
Q

Colour of Fe2+ in solution

A

Pale green

35
Q

Colour of Fe3+ in solution

A

Yellow

36
Q

Colour of Cu2+ in solution

A

blue

37
Q

Give 2 examples of bidendate ligands

A
  • ethandioate
  • ethane-1,2-diamine.
38
Q

Give one example of a multidentate ligand

A
  • EDTA4- (can form 6 coordinate bonds)
39
Q

Define the term coordination number

A
  • number of coordinate bonds in a complex.
40
Q

What is the relationship of the size of ligand and coordination number?

A
  • larger the ligand, the smaller the coordination number would be (fewer ligands can fit around the central metal ion)
41
Q

what shape is cisplatin? describe its structure and its use

A
  • Pt in the middle
  • 2 Cl ligands
  • 2 ammonia ligands
  • square planar (2 LP, 4BP)
  • anti-cancer drug
42
Q

How to work out oxidation state of central metal ion in ligand complex?

A

total oxidation state of complex-total oxidation state of ligands

43
Q

What is redox potential?

A

a value that tells us how easily an ion is reduced.

44
Q

Why might there be a difference in redox potential to the standard values and values in a data book?

A
  • environment the ions might have been in could have been different.
45
Q

if Cu has a E0 value of +0.34, and Zn has a E0 value of -0.76, what does this imply in terms of redox potentials? Explain.

A
  • means that Cu is less stable than Zn.
  • because the least stable ions have the largest redox potentials, so more likely to be reduced.
46
Q

When is a redox reaction feasible?

A

when E0 is positive

47
Q

how do you know if a species is going to be likely reduced?

A
  • its reduction potential (or E0) is more positive.
48
Q

Explain why transition metals are good catalysts

A
  • they are capable of changing oxidation states.
  • thus they can bind to reactants, forming intermediates in a pathway with a lower activation energy.
49
Q

Describe the contact process in terms of the catalytic activity.

A
  • used to conver t sulphur dioxide to sulphur trioxide
  • uses vanadium oxide catalyst
  • vanadium will be reduced, then re-oxidised
  • V2O5 reacts with SO2 to give SO3 and V2O4
  • V2O4 then reacts with oxygen to reform V2O5
50
Q

in what case would a Cr3+ appear green?

A
  • if one or more of the water ligands in solution is substituted with
51
Q

what does amphoteric mean

A
  • can act as an acid and a base
52
Q

Describe what happens to the {Cr(H2O)3(OH)3} complex when put in acidic and basic solution

A
  • when acid is added, it will act as a base and accept H+ ions to form the [Cr(H2O)6]3+ complex again.
  • when an alkali is added, it will act as an acid and donate H+ ions to the OH ions to form water.
53
Q

What will occur if excess ammonia is added to the [Cr(H20)3(OH)3] complex? give the equation.

A
  • ligand substitution will occur.
  • [Cr(H20)3(OH)3] + 6NH3 —> [Cr(NH3)6]3+ + 3H2O + 3OH-
54
Q

give the equation and colour changes for oxidising the [Cr(OH)6]3- complex ions with hydrogen peroxide in alkaline solution.

A
  • Green to yellow
  • 2[Cr(OH)6]3- + 3H2O2 —-> 2OH- + 2CrO42- + 8H20
55
Q

Give the equation for equilibrium between chromate and dichromate ions
give the colour

A
  • 2CrO42- + 2H+ —> Cr2O72- + H2O
  • orange
56
Q

Relationship between entropy and stability of a complex

A
  • the higher the entropy, the more stable the complex
57
Q

Describe the chelate effect

A
  • when monodentate ligands and subbed in by bidendate/multidentate ligands, which leads to a solution with more particles in it, leading to an increase in entropy.
58
Q

colour change for Cu2+ for
- aq solution
- small amount of OH- and NH3
- excess OH-
- excess NH3

A
  • blue
  • pale blue
  • no change
  • dark blue
59
Q

colour change for Fe2+ for
- aq solution
- small amount of OH- and NH3
- excess OH-
- excess NH3

A
  • Pale green
  • dirty green
  • no change
  • no change
60
Q

colour change for Fe3+ for
- aq solution
- small amount of OH- and NH3
- excess OH-
- excess NH3

A
  • Yellow
  • orange
  • no change
  • no change
61
Q

colour change for Co2+ for
- aq solution
- small amount of OH- and NH3
- excess OH-
- excess NH3

A
  • pale pink
  • blue
  • no change
  • brown-yellow
62
Q

what is the relationship between charge and solubility of complex ions?

A
  • if charged, it is soluble.
63
Q

State the colour change and equation of the [Co(H2O)6]2+ with excess NH3

A
  • pink to straw colour
  • [Co(H2O)6]2+ + 6NH3 —-> [Co(NH3)6] 2+ +6H2O
64
Q

State the colour change and equation of the [Cu(H2O)6]2+ with excess NH3

A
  • Blue to dark blue
    -[Cu(H2O)6]2+ + 4NH3 —-> [Cu(NH3)4(H2O)2] 2+ +4H2O
65
Q

State the colour change and equation of the [Co(H2O)6]2+ with Cl-

A
  • [Co(H2O)6]2+ + 4Cl- —> [CoCl4]2- + 6H2O
  • goes from pink to blue.
66
Q

State the colour change and equation of the [Cu(H2O)6]2+ with Cl-

A

-[Cu(H2O)6]2+ + 4Cl- —> [CuCl4]2- + 6H2O
- goes from blue to yellow

67
Q

State the colour change and equation of the [Fe(H2O)6]2+ with Cl-

A

[Fe(H2O)6]3+ + 4Cl- —> [FeCl4]- + 6H2O
- stays yellow.

68
Q

What are the shapes of the Chloride sub complex ions

A
  • tetrahedral
69
Q

Describe the observations when aqueous sodium hydroxide is added drop by drop until in
excess to a solution of chromium(III) ions.

A
  • first green ppt will form
  • ppt will then re-dissolve to form a green solution
70
Q

Two factors that affect the colour of the solution are the oxidation number of the
central metal ion, and the ligands present.
Give examples to illustrate these factors by referring to complex ions
of iron and/or copper. Include the formula and colour of each complex.
An explanation of why transition metal ions are coloured is not required

A
  • eg [Fe(H2O)6])2+ is green in solution, but [Fe(H20)6]3+ is yellow in solution
  • but [Cu(Cl)4]2- is yellow in solution, but [Cu(H2O)6]2+ is blue in solution.
71
Q

Explain why the complex ions [Co(NH3)6]
2+ and [Co(H2O)6]
2+ are coloured and have
different colours.

A
  • ligand bonding causes d-orbital splitting
  • the energy difference is dependant on the ligand that is bonding
  • difference in energy leads too different wavelengths of light being absorbed
  • so the unabsorbed wavelengths of light are transmitted.
72
Q

in terms of ionisation energies, why might oxidation numbers change?

A
  • because there is a gradual increase in ionisation energies.
73
Q

Describe the observations when aqueous sodium hydroxide is added drop by drop until in
excess to a solution of chromium(III) ions.

A
  • green ppt
  • re-dissolves to form a green solution
74
Q
A

Edexcel Chemistry A level (18 decks)

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