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AQA A-Level Chemistry > 3.2.5 Transition metals > Flashcards

3.2.5 Transition metals Flashcards

1
Q

What is a transition metal ?

A

Elements in the d-block of the periodic table with a partially filled d-orbital

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2
Q

Name 4 typical properties of transition metals

A

High boiling point
High melting point
Strong/ hard
High density

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3
Q

Transition metals form complexes, what is a complex ?

A

A central ion or atom surrounded by ligands

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4
Q

What is a ligand?

A

A molecule or ion that forms a co-ordinate bond with a transition metal by donating a pair of electrons

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5
Q

What is a coordination number?

A

The number of co-ordinate bonds formed around the central metal ion

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6
Q

What is the co-ordination number in this ligand [Co(H2O)6]2+

A

6

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7
Q

What properties do NH3 and H2O share which means they can be exchanged via a ligand substitution reaction ?

A

They are similar in size and both uncharged.

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8
Q

Why would a Cl- ion result in a change of co-ordination number when undergoing a substitution reaction with NH3 or H2O ?

A

As Cl- is much larger than H2O and NH3 because it is a charged ion

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9
Q

Complexes with only Cl- ions always have a co-ordination number of…..? What shape does this produce?

A

Cl- ions always have a coordination number of 4 producing a tetrahedral shape. (As the ion is bigger only 4 can fit around central metal ion)

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10
Q

Give 3 examples of monodentate ligands

A

H20, NH3, Cl-

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11
Q

What is a monodentate ligand ?

A

Ligands that form one co-ordinate bond with a central metal ion.

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12
Q

What is a bidentate ligand ?

A

Ligands that can form 2 co-ordinate bonds with a central metal ion as they have 2 lone electron pairs.

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13
Q

Give 2 examples of bidentate ligands

A

Ethanedioate
Ethane-1,2-diamine

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14
Q

Where are the lone pairs located on an ethanedioate ion?

A

The lone pairs are located on two of the oxygen atoms with single bonds.

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15
Q

Where are the lone pairs located on a molecule of ethane-1,2-diamine

A

The lone pairs are located on each of the nitrogen atoms

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16
Q

What is a multi dentate ligand?

A

Ligands that form up to 6 co-ordinate bonds with the central metal ion

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17
Q

Give an example of a multi dentate ligand and give its charge

A

EDTA 4-

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18
Q

What type of ligand is found in Haemoglobin and what TM ion is present with how many co-ord bonds ?

A

Haem- a multi dentate ligand as it has 6 co-ordinate bonds around the central Fe2+ ion

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19
Q

Why is carbon monoxide toxic to humans ?

A

As it replaces the oxygen in the haem complex preventing from it being transported around the body

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20
Q

What is the chelate effect ?

A

When bidentate and mulitdentate ligands replace mondentate ligands to form complexes.

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21
Q

Why is the enthalpy change for ligand substitutions very small ?

A

As the bonds being broken are very similar to the bonds being formed. Therefore the overall energy change is near 0.

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22
Q

Complexes with H2O and NH3 ligands often form ____ shapes ?

A

Octahedral

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23
Q

What bond angle is found in octahedral complexes ?

A

90 degrees

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24
Q

What is Cis isomerism ?

A

When two ligands are next to each other (Zame Zide)

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25
Q

What is trans isomerism ?

A

When two ligands are opposite to each other

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26
Q

What type of isomerism is commonly found with bidentate ligands in octahedral complexes ?

A

Optical isomerism, They are two mirror images of each other

27
Q

Larger ligands such as Cl- form a different shape, what is that shape and name bond angle ?

A

Tetrahedral shape with a bond angle of 109.5 degrees

28
Q

Can tetrahedral complexes show optical isomerism ?

A

Yes they can

29
Q

What shape complexes do platinum and nickel form and state bond angle ?

A

Square planar with a bond angle of 90 degrees

30
Q

How many co-ordinate bonds do platinum and nickel form ?

A

4 co-ordinate bonds

31
Q

What shape complexes does Ag (silver) form and state bond angle ?

A

Linear with a bond angle of 180 degrees

32
Q

What type of complex is present in [Ag(NH3)2]+ (Tollens reagent) ?

A

Two co-ordinate bonds with a bond angle of 180 degrees forming a linear shape

33
Q

What is Cisplatin, and what is it most commonly used for ?

A

This is the cis isomer of a square planar complex of platinum. It is most commonly used as a cancer therapy drug.

34
Q

What are some of the side effects of using cisplatin and what can be done to reduce this ?

A

It can cause serious side effects such as hairloss so must be administered in small amounts to try to minimise this.

35
Q

What 3 things affect the colour of a transition metal ion ?

A

Co-ordination number
Type of ligand
Oxidation state

36
Q

How does colour arise in transition metal ions ?

A

When some of the wavelengths of visible light are absorbed and the remaining wavelengths of light are transmitted or reflected

37
Q

Electrons in the d-orbital exist in a number of ___?

A

Energy states

38
Q

Name 2 energy states electrons are found in the d-orbitals ?

A

Ground state and excited state

39
Q

What symbol is used to measure energy changes between ground and excited state ?

A

Delta(triangle) E

40
Q

State the equation used to calculate energy change between states

A

Delta(triangle) E = hc/ wavelength = hv

41
Q

What does h stand for in the equation Delta(triangle) E = hc/ wavelength = hv ?

A

h= Placks constant

42
Q

What does v stand for in the equation Delta(triangle) E = hc/ wavelength = hv ?

A

v= Frequency

43
Q

What is colorimetry ?

A

An ​analytical technique​ that uses the ​absorption​ of visible light to determine the concentration​ of coloured ions by measuring absorbance.

44
Q

What two things are plotted on a calibration graph ?

A

Relative absorbance against concentration

45
Q

How many oxidation states does vanadium have and what are they ?

A

Vanadium has 4 different oxidation states: They are +5, +4, +3 and +2

46
Q

What is the oxidation number of VO2^+ and what colour is the ion ?

A

+5 , Yellow

47
Q

What is the oxidation number of VO2+ and what colour is the ion ?

A

+4, Blue

48
Q

What is the oxidation number of V3+ and what colour is the ion ?

A

+3, Green

49
Q

What is the oxidation number of V2+ and what colour is the ion ?

A

+2, Violet

50
Q

What is a useful pneumonic to remember colour of Vanadium ions ?

A

You better get vanadium

51
Q

What is the complex [Ag(NH3)2]+ used to test for ?

A

Distinguish between Aldehydes and ketones

52
Q

Give the half equation for the reduction of MnO4- to Mn2+

A

MnO4- + 8H+ + 5e- —> Mn2+ + 4H2O

53
Q

What is a catalyst ?

A

A catalyst is a substance that ​speeds up the rate of a reaction​ ​without being used up​ in the reaction. It provides an alternative reaction path with a lower activation energy.

54
Q

Does the use of a catalyst affect the position of an equilibrium ?

A

Catalysts don’t affect the position of equilibrium but allow it to be ​reached faster

55
Q

What is a heterogeneous catalyst ?

A

These are catalysts that are in a ​different phase or state ​to the species in the reaction.

56
Q

Give an example of a heterogeneous catalyst used in a reaction

A

An example of this is the Haber Process, where a ​solid iron catalyst ​is used to speed up the reaction between hydrogen and nitrogen gases.

57
Q

Why do transition metals make good catalyst and how ?

A

As they have variable oxidation states, ​Electrons are transferred​ to produce a ​reactive intermediate ​and speed up the reaction rate.

58
Q

Give an example of a transition metal acting as a hetrogenous catalyst

A

An example of this is the ​Contact Process​ which uses a vanadium oxide catalyst to speed up the conversion of sulfur dioxide to sulfur trioxide.

59
Q

What is a homogenous catalyst ?

A

These are catalysts that are in the ​same phase​ to the species in the reaction.

60
Q

Give an example of a homogenous catalyst

A

The reaction between S2O8^2- and I- ions with an Fe2+ catalyst

61
Q

What is catalyst poisoning and what type of catalyst is more commonly affected ?

A

Heterogeneous catalysts can be ​poisoned by impurities​ which ​block the active sites​ and prevent adsorption​. Therefore the bonds of the molecules remain strong and the catalyst has no effect on the rate of the reaction.

62
Q

What is a co-ordinate bond ?

A

A type of covalent bond that is formed by sharing of an electron pair from a single atom.

63
Q

What is autocatalysis ?

A

When on elf the products of the reaction can act as a catalyst for the reaction

AQA A-Level Chemistry (36 decks)

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