Chapter 23: Transition Metals Flashcards

1
Q

Define a transition metal.

A

Forms an ion with a part full d sub shell of electrons.

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2
Q

What are the four main features of transition metals?

A
  • Variable oxidation states
  • Colour
  • Catalysis
  • Complex formation
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3
Q

When is a complex ion formed?

A

When a transition metal ion is surrounded by ions or other molecules, to collectively form Logan’s.

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4
Q

Define a ligand.

A

An ion or molecule with a lone pair of electrons that forms a coordinate bond with a transition metal.

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5
Q

Define co-ordination number.

A

The number of co-ordinate bonds to ligands that surround the d-block metal ion.

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6
Q

Is chlorine or ammonia a bigger ligand?

A

Chlorine is a bigger ligand, so fewer ions fit around the central ion.

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7
Q

Define multidentate ligands.

A

Have more than one atom with a lone pair of electrons which can bond to a transition metal ion.

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8
Q

Example of a multidentate ligand.

A

EDTA^-4

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9
Q

What is EDTA^-4?

A

Acts as a hexadentate ligand.

Uses lone pairs on four oxygen atoms and both nitrogen atoms.

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10
Q

What is a use of chelates?

A

Effectively remove d-block metal ions from solution.

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11
Q

What are chelates?

A

Complex ions with polydentate ligands.

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12
Q

Examples of bidentate ligands.

A

Ethanedioate ion.
Benzene-1,2-diol
Ethane-1,2-diamine

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13
Q

What are aqua ions?

A

When you dissolve the salt of a transition metal in water, the positively charged metal ion becomes surrounded by water molecules acting as ligands.

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14
Q

Why are transition metal compounds complexes formed?

A

1) They have part filled d-orbitals.
2) It is possible for electrons to move from one d-orbital to another.
3) In an isolated transition metal ion, all d-orbitals are of exactly the same energy, but in a compound the presence of other atoms nearby makes the d-orbitals have slightly different energies.
4) When electrons move from d-orbital to another of higher energy level. They often absorb energy in the visible region of the spectrum equal to the difference in energy between levels.
5) This colour is missing from the spectrum and you see the combination of colours that are not absorbed.

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15
Q

How does colorimetry work?

A

A light source and detector is used it measure the amount of light of a particular wavelength that passes through a solution. The more concentration the solution is, the less light is transmitted though the solution

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16
Q

What are heterogeneous catalysts?

A

Present in a reaction in a different phase than the reactants. Usually present as a solid.

17
Q

How to make heterogeneous catalysts more efficient?

A
  • Increase surface area.
  • Spread the catalyst onto an inert support medium or impregnate it into one. (Increases the surface area to mass ratio so little goes a long way).
18
Q

Why do catalysts not last forever?

A
  • Over time, surface becomes covered in unwanted impurities and becomes poisoned.
  • Finely divided catalyst may gradually be lost from the support medium.
19
Q

What is a homogenous catalyst?

A

When catalyst is in the same phase as they reactant. An intermediate is formed.

20
Q

Give two examples of heterogeneous catalysts.

A

Hater process.

Contact process.

21
Q

What is used as the catalyst in the haven process?

A

Iron- Lasts five years before becoming poisoned by impurities in the gas stream.

22
Q

What is made is in haber process?

A

Ammonia is mad from nitrogen and oxygen.

23
Q

What is produced in the contact process?

A

Sulphuric acid.

24
Q

How is sulphuric acid made?

A

Sulphur, oxygen and water.

2SO2 + O2 <=> 2SO3

25
Q

2SO2 + O2 <=> 2SO3

What is this reaction catalysed by?

A

Vanadium oxide.

V2O5

26
Q

(1) Vanadium (V) oxide oxidises … to … and itself is reduced to …
(2) Then, the … is oxidised back to vanadium (V) oxide by …

A

(1)Sulphur dioxide
Sulphur trioxide
Vanadium (IV) oxide
SO2 + V2O5 -> SO3 + V2O4

(2) Vanadium (IV) oxide
Oxygen
2V2O4 + O2 -> 2V2O5

27
Q

Example of homogenous catalysis by transition metals.

A

Peroxodisulfate ions oxidise iodide ions to iodine.
Catalysed by Fe2+ ions.
S2O8^-2 + 2I- -> 2SO4^2- + I2

28
Q

Two steps of the oxidation of iodide ions to iodine.

A

(1) Peroxodisulphate ions oxidise iron (II) to iron (III).

(2) Then, Fe3+ oxidises the I- to I2, regenerating the Fe2+ ions so that none are used up in the reaction.

29
Q

What is autocatalysis?

A

One product of the reaction is the catalyst for the reaction.

The reaction starts slowly, as it is uncatalysed. As the concentration of the product builds up, reaction increases to the catalysed rate.