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A2 Chemistry > Transition Metals > Flashcards

Transition Metals Flashcards

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1
Q

What are d block elements

A

their highest energy electrons are in the d orbital

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2
Q

What are transition metals

A

An element which forms at least one stable ion with a partially full d-shell of electrons

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3
Q

What are the characteristics of transition metals

A
  • form complexes
  • form coloured ions
  • variable oxidation states (they have partially filled d orbitals so can lose 4s and 3d electrons)
  • catalytic activity
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4
Q

Why is zinc not a transition metal

A

It can only form a 2+ ion. In this ion the Zn2+ has a complete d orbital

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5
Q

What is a complex

A

A central metal ion surrounded by ligands

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6
Q

What is a ligand

A

An atom, ion or molecule which can donate a lone electron pair to form a dative covalent bond

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7
Q

What is the coordination number

A

The number of dative covalent bonds a ion is forming

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8
Q

Explain why complexes formed from transition metal ions are coloured

A
  • some wavelengths of light are absorbed
  • to promote electrons in the d orbitals to higher energy levels
  • the light that is not absorbed is transmitted to give the substance colour
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9
Q

AE = ?

A
  1. plancks constant x frequency of light absorbed
  2. plancks constant x speed of light/wavelength of light absorbed
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10
Q

Give 3 examples of catalysts and the reactions they catalyse

A

Iron - Haber process
Vanadium (V) oxide - contact process
MnO2 - decomposition of H2O2

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11
Q

Which electrons do transition metals lose first when forming ions

A

4s

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12
Q

How many coordinate bonds does EDTA form

A

6

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13
Q

When a compound is dissolved in water what shape does it form

A

Octahedral with 6 H20 Ligands

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14
Q

Explain the chelate effect in terms of entropy

A
  • multidentate ligands = more molecules
  • so significant increase in entropy
  • delta G is less than 0
  • so reaction is feasible
  • more stable complex ion formed
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15
Q

What shape is Platin

A

Square planar - forms Cisplatin

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16
Q

How does haemoglobin transport oxygen

A

Oxygen forms a coordinate bond to Fe(II) in haemoglobin, allowing it to be transported in the blood

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17
Q

Why is carbon monoxide toxic

A

It replaces oxygen coordinately bonded to Fe (II) in haemoglobin

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18
Q

What is the chelate effect

A

Bidendate and multidentate ligands replace monodentate ligands from complexes

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19
Q

How would changing a ligand or coordination number change colour

A

It will alter the energy split between the d orbitals, changing AE and the frequency of light absorbed

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20
Q

What can be used to reduce Vanadium

A

Zinc

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21
Q

What colour is MnO4-

A

Deep purple

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22
Q

What colour is Mn2+

A

Pink

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23
Q

What colour is Cr2O7 2-

A

Orange

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24
Q

What colour is Cr3+

A

Green

25
Q

What colour is Fe2+ aqua ion

A

Green

26
Q

What colour is Fe3+ aqua ion

A

Pale brown

27
Q

What colour is Cr2+ aqua ion

A

Blue

28
Q

What colour is Cr3+ aqua ion

A

Red/violet

29
Q

What colour is Co2+ aqua ion

A

Brown

30
Q

What colour is Co3+ aqua ion

A

Yellow

31
Q

Why are transition metals good catalysts

A

They can exist in variable oxidation states so can provide alternative pathways easily

32
Q

What are the 2 equations for vanadium catalyst in the contact process

A

SO2 + V2O5 —> SO3 + V2O4
2V2O4 + O2 —> 2V2O5

33
Q

Describe how a heterogeneous catalyst works

A
  • the reactants adsorb onto the surface/active sites
  • the bonds weaken and reaction takes place
  • the products desorb from the surface
34
Q

Describe how to obtain a calibration graph

A
  • measure absorbance for a range of known concentrations
  • plot a graph of absorbance vs concentration
  • read the value of concentration for the measured absorbance from the graph
35
Q

Explain why a compound may be white

A
  • full 3d subshell
  • so can’t absorb visible light
36
Q

Why might the enthalpy change/AH for a reaction be (almost) 0

A

Same number and type of bond being broken and made

37
Q

Define autocatalysis

A

When the product of a reaction is also a catalyst for that reaction

38
Q

Write two equations to show how Fe2+ catalyses the reaction between S2O8(2-) ions and I- ions

A

S2O8 (2-) + 2Fe2+ —> 2Fe3+ + 2SO4 (2-)
2 Fe3+ +2I- —> 2Fe2+ + I2

39
Q

Define homogenous vs heterogenous catalyst

A

Homogeneous catalyst is in the same phase as reactants
Heterogeneous catalyst is in a different phase from the reactions

40
Q

What is a Lewis acid and base

A

Acid - electron pair acceptor
Base - electron pair donor

41
Q

What colour is V3+

A

Green

42
Q

What colour is V2+

A

Violet

43
Q

What colour and oxidation state is VO2 (+)

A

5+
Yellow

44
Q

What colour and oxidation state is VO (2+)

A

4+
Blue

45
Q

How could a compound increase the pH

A
  • has a high charge density
  • so polarise water molecules more
  • so weakens the OH bond in water, releasing H+ ions
46
Q

What are the monodentate ligands

A

H20, NH3 and Cl-

47
Q

If CuCl2 solid is dissolved in solution what is its Ligand

A

[Cu(H20)6] 2+

48
Q

What are the two bidentate ligands

A
  1. Ethane-1,2-diamine
    NH2CH2CH2NH2
  2. Ethanedioate
    C2O4 (2-)

Both form 2 coordinate bonds

49
Q

What is the multidentate ligand called

A

EDTA (4-)
Forms 6 coordinate bonds

50
Q

Explain Cl- effect on the coordination number when it reacts

A

It decreases eg from 6 to 4
Because Cl- ions are larger so only 4 can fit around the metal ion

51
Q

What is Cis-trans isomerism

A

Occurs in monodentate Ligands
E-Z isomerism
Trans - E
Cis- Z

52
Q

What type of isomerism occurs in bidentate ligands

A

Optical isomerism

53
Q

Describe why optical isomerism occurs

A

The arrangement of the coordinate bonds can lead to enantiomers formed

54
Q

What two factors effect the lifetime of a catalyst

A
  • catalyst poisoning - active sites blocked
    + large surface area eg by using powder or small pellets
55
Q

Describe a ligand reaction in Gibbs terms in which the no. Of molecules increases

A
  • increase in entropy as more moles of products than reactants
  • so more disorder
  • delta S is positive
  • delta G is negative so reaction is feasible (write equation to work out AG)
  • delta H is close to 0 because same number and type of of bonds
56
Q

Why might a reaction be slow before a catalyst is added

A

If there are two negative ions that repel
It will make the activation energy higher

57
Q

Why might a ion not be able to catalyse a reaction

A
  • doesn’t have a variable oxidation state
58
Q

Why might two atoms be a good catalyst

A

Because the two oppositely charged ions attract each other

A2 Chemistry (16 decks)

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