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A-LEVEL CHEM > A2- Transition Metals > Flashcards

A2- Transition Metals Flashcards

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1
Q

What are 4 general properties of transition metals?

A
  • form coloured ions
  • form complexes
  • variable oxidation states
  • act as catalysts
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2
Q

What is a Ligand?

A

a species that can donate a pair of electrons to a central metal ion, forming a coordinate bond

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3
Q

What is meant by the term coordination number?

A

the number of co-ordinate bonds to the central metal atom or ion

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4
Q

What shape and bond angle does a complex with H2O ligands have?

A

Octahedral, 90

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5
Q

What shape and bond angle does a complex made with Cl have?

A

tetrahedral, 109.5

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6
Q

What is a bidentate ligand? give an example

A

a ligand that forms 2 coordinate bonds with the central metal atom
- diaminoethane
- ethanedioate

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7
Q

Why do transition metals share the same 4 general properties?

A

incomplete d-subshell

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8
Q

Why does Cl- form a tetrahedral complex?

A

larger ions

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9
Q

Give 3 examples of monodentate ligands

A

H2O, NH3, Cl-

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10
Q

What is a monodentate ligand?

A

a ligand that makes only one coordinate bond to the central metal ion or atom

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11
Q

Give an example of a multidentate ligand

A

EDTA4-

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12
Q

What are ligand substitution reactions?

A

reactions where ligands around a complex ion are substituted by other ligands

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13
Q

What is a complete ligand substitution with no change in coordination number?

A

a reaction where all ligands are substituted by new ones. Ligands must be a similar size

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14
Q

Why do complete ligand substitutions with no change in coordination number have small enthalpy changes?

A

small bond energies of ligands are similar

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15
Q

What is a complete ligand substitution with a change in coordination number?

A

a reaction where all ligands are substituted by new ones, ligands are different size

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16
Q

What is an incomplete ligand substitution with no change in coordination number?

A

only some ligands substituted but number of coordinate bonds stays the same

17
Q

Why do multidentate ligands form thermodynamically stable compounds?

A
  • very small enthalpy change as 6 C-O are broken and 6 are formed
  • large entropy change as more species are produced
  • very negative free energy change
18
Q

Give an example of a Vanadyl (V) species…
What colour is this?

A

VO2 +
Yellow

19
Q

Give an example of a Vanadyl (IV) species…
What colour is this?

A

VO 2+
Blue

20
Q

Give an example of a Vanadium (III) species…
What colour is this?

A

V 3+
Green

21
Q

Give an example of a Vanadium (II) species…
What colour is this?

A

V 2+
Purple

22
Q

Why is +2 a common oxidation state?

A

2 electrons lost from 4s sub-shell

23
Q

Which transition metal electron configurations are more stable than others?

A

those with a half-filled d sub-shell

24
Q

How can Vanadium species be reduced?

A

heating with Zn metal

25
Q

How can Vanadium species be oxidised?

A

oxidising agents such as manganate (VII) solution

26
Q

What affects the redox potential of transition metals?

A
  • pH
  • type of ligands
  • conditions (temp, pressure and conc)
27
Q

What are redox titrations?

A

titrations based on change in oxidation states

28
Q

Give the equation for the redox titration between Iron (II) and Manganate (VII)

A

5Fe2+ + MnO4- + 8H+ –> Mn2+ + Fe3+ + 4H2O

29
Q

What colour change occurs in the redox titration between Iron (II) and Manganate (VII)?

A

colourless to pink

30
Q

Give the equation for the redox titration between ethanedioate and Manganate (VII)

A

5C2O42- + 2MnO4- + 16H+ –> 10CO2 + 8H2O + 2Mn2+

31
Q

What is the chelate effect?

A

complexes with multi-dentate ligands are favoured over complexes with monodentate ligands, due to the the large increase in entropy

32
Q

Why can HCl NOT be used in the redox titration between Iron (II) and Manganate (VII)?

A

Cl- ions will be oxidised by the manganate ions

33
Q

How do you convert from nm to m?

A

x 10-9

A-LEVEL CHEM (62 decks)

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